When leading a formation flight, I issue a "Sharpie Flight OPS CHECK" every 30 minutes. The 496's timer cues me on that one.
But as far as switching tanks goes, I burn off fuel to keep the aileron trim centered. Any time you've got aileron trim in, that's DRAG. Trim is deflecting controls to resolve an imbalance. If you want peak speed and/or economy, you gotta keep those control surfaces IN TRAIL.
When I have the TruTrak autopilot engaged, it's a great indicator of when to switch tanks. When everything is in trim, you don't see the stick move. But if there's a fuel imbalance (heavy wing) you can see the stick "pulsating" every few seconds. I disable the autopilot to confirm a wing is heavy, and then I switch tanks. It typically works out to 30-40 minutes at 7 gph.
On really long legs, where I want to maximize my range, I need to keep an exact tally of how much fuel I have in each tank (because I don't trust my quantity indications). I burn from the heavy side first, and I start a written table in my little notepad. It starts out like:
L R Total
21.0 (21.0) 42.0
and I circle whichever side I'm burning from (i.e. above, I'm burning off the right).
So let's say 30 minutes later I have a heavy wing and switch tanks. Then again, and again. After a while, the table looks like this:
L R Total
21.0 (21.0) 42.0
(21.0) 17.5 38.5
16.8 (17.5) 34.3
(16.8) 13.1 29.9
13.3 (13.1) 26.2
etc.
At the end of a 4:45 leg, I have a pretty darn near exact idea of how much fuel is left in each tank.
Anyway, that's my technique for long trips. It's also a GREAT hypoxia indicator. If I have any trouble doing simple math, I turn the O2 up. I also use a pulse oximeter, but that's another thread...
