I'm not sure you need to recalibrate every few months...
...unless you are tracking like 24/7 throughout that time period...or if you are swapping tape formulations.
Heads don't wear THAT fast and neither to the tape guides...and the electronics should stay pretty stable over that time period...and screws rarely turn by themselves!
I would maybe toss up a test/calibration tape every few months and just see if your levels are where they should be going in/out. If they are...not need to recalibrate. Pulling cards and moving adjustment pots and wires on old deck can sometimes open up a can of worms.
And also...don't demag constantly...unless of course you're really putting some serious 24/7 type of hours on your deck like a commercial facility might be.
Best thing is to have a Gauss meter...and check how much magnetism has built up.
Often you will find it's nominal for moderate home/project studio use....
…so no need to demag unless you just like doing it!

Cleaning is the thing to do regularly/daily...even sometimes during tracking sessions...especially of you older/questionable tape. You don't need a drop out on some important section of a lead vocal...etc.
Also...the 911 is my favorite formulation for tracking...the 468 is great too, but I would use that more for mixdown/mastering, though I use 911 for that too...and they are so close, that you don't necessarily need to recalibrate when switching between them.
US Recording has new RMGI 911 tape at decent prices.
http://usrecordingmedia-store.stores.yahoo.net/