Here’s a good place to start: https://support.formlabs.com/s/topic/0TO1Y000000IvrlWAC/maintaining-the-form-2-form-2
Be aware the exact guidance has evolved over the years and you may notice some minor documentation discrepancies depending where you look.
In the LT tank article, Formlabs recommends against storing resin in LT tanks for more than 3 months. For long-term storage of dispensed resin, they recommend pouring resin into a separate, opaque container (e.g. wide-mouth opaque HDPE or polypropylene bottles).
In another article, they state Standard resin tanks (the ones with PDMS) last 1000-3000 layers of printing or 3 months, and that LT tanks should last twice that (which means up to 6000 layers / 6 months). There are exceptions for some of the more aggressive resins (e.g. engineering ones), where LT tanks are mandatory, and don’t extend the lifetime.
You can find general guidance on materials here: https://support.formlabs.com/s/topic/0TO1Y000000IvumWAC/materials-overview-form-2
And use the dropdown to read about specific resins (the “Using ___ Resin” ones are where you’ll notice specific guidelines / limitations).
All that said, I’ve personally stored various resins in tanks for over a year with no ill-effects (dark, room temperature, periodic mixing). If things have been sitting for a long time, it’s really important to stir them up well (using the metal spatula that has rounded edges, or a plastic one). The components can separate over time - e.g. I’ve noticed Black stratifies into a gooey layer at the bottom of the tank and less viscous one on top). If you’re patient and gently stir for long enough it becomes homogeneous again.
It sounds like the previous caretaker was meticulous, but it wouldn’t hurt to filter each resin through a ~190 micron paint strainer to catch any debris that might be left behind from previous print failures or partial failures (obviously use a new strainer for each different resin).
When you drain the tanks it’s also a good opportunity to inspect them for any visible damage, clouding or leaks (here are some photos). Any smudges or dust on the bottom (outside) of a tank’s optical window can be cleaned with a quick spritz of Novus #1 and a microfiber cloth. Avoid touching the interior of the window with anything but the spatula.
Never use IPA or other chemicals on a tank! It can cause the acrylic to crack or fatigue. As far as I know that also applies to LT tanks. Here’s a quick chart showing what products are appropriate for cleaning which components.
I’d also recommend shaking your cartridges for a good 10 minutes each. Shelf life of cartridges was increased a while back, I think most resin expires about 2 years from the manufacture date seen on the label, but some like Tough 1500 are shorter - you can find a full list here.
If dust may have collected, it could be worth inspecting and cleaning the printer’s glass optical window.
Since you don’t have a lot of experience yet with the printers, I’d pick up at least one brand new cartridge and tank to use for a test print. If you run into troubles, that will help you to quickly rule out old consumables / resin as a factor.
This page lists various print defects that can occur and how to diagnose and resolve them.
I’ve noticed over time, contaminants build up inside the optical chamber - on the main mirror, and sometimes even galvo mirrors. Dirty optics is a common cause of print issues (such as poor adhesion, ragging, etc). Before inspecting or attempting to clean the interior you’d need to contact Support. They can help you determine if cleaning is necessary (doing it too often can wear the first-surface mirrors) and provide official documentation on the procedure.
Once you know the printer itself is working, do a test print with each tank to see if the resin still produces good results (the built-in “butterflies” STL file is good for this and completes fast). I’d bet a lot of the resins are still completely fine. Of course if you don’t have time or want to be sure, and cost isn’t an issue, then you could always get rid of them all and buy new.
You’ll also want to top off the Form Wash with fresh IPA, or if it’s been sitting for a long time with dissolved resin in it, replace its IPA altogether.
You don’t need to re-calibrate after moving the printer. But if you want to, here’s some info on fine-tuning, and various users have created templates/models/spreadsheets to help (here’s one).
Here’s a great teardown if you want to know more about the internals of the printer without ripping your own apart: https://www.bunniestudios.com/blog/?p=4641
Finally, consider grabbing a copy of any of the above support articles that you find helpful (or snapshotting them with WayBackMachine or archive.is) along with any field guides you obtain from Support, before the Form 2 gets sunsetted in 2023. I noticed after the Form 1+ went end of life, a lot of the documentation disappeared from the website or became harder to find.
Have fun printing! The Form 2 is a great printer and fairly user-friendly.