All the heads you mention are good heads. I am a firm believer in single ply coated on the snare - and the Ambassador is certainly the industry standard. Pinstripes have been the standard for 2-ply for a long time as well.
Since I work in a drum shop, I try alot of stick and head combinations, but what I've been useing recently are:
Evans - Coated, 1ply Dry Vent on the snare, Clear G1 or G2 (depending on sound I'm looking for) on toms and recently Emad for the kick (although I like the EQ3 & EQ4 as well). I was at the Evans factory in 2000 and was impressed with quality control (Evan's had gone downhill before Di'Ardario took over).
Aquarian make really good heads (some may say the best heads), but their distribution is weak - so it can be harder to find all the sizes you need (in local stores at least).
As far as changing heads, obviously it is relavant to how much you hit the drums, etc. I normally change the snare batter every 3 months, the tom batters every 6 months and the kick batter every couple of years. I only change bottom heads every few years.
Of course, if the sound has been compromised I may change resonant heads more often. I'm lazy when it comes to changing heads, and I've got 3 accoustic kits I use fairly often, so I have to be somewhat selective on how often I want to commit.
Actually, now that I think of it, I change my drum heads more often than I change my guitar strings - or my socks for that matter.
