I get usually about 10 years out of a reciever or transmitter battery. Most
times I just charge them overnight before a day of flying, usually about 12 hours
or so. I have friends with the fancy battery "cycle features" and such. Their
batteries only last about 3-4 years....go figure.
You are pushing it! Regardless of how many time a battery is charged, the internal cell seperator deteriorates with age. The more cells you have in series, the faster this occurs. The mean time to failure for a 4-5cell pack is supposed to be 3-5 years, and for an 8 cell TX pack, it is around 2-3 years. Failure is defined as the battery's capacity dropping below 80% of rated... it is a sign of an impending internal short. Another sign is a high self discharge rate... if you charge a cell and let it sit for a week then discharge it and you find the capacity is very low, you have an impending failure. Of course, if you never check your batteries under load and you use 5-cell packs, you may get away with a keeping RX batteries longer (i.e. your RX will function), but you are flirting problems.
I know you said you get 10 years, but I think if you were to do a capacity check on an 8 year old battery you'd find it to be in terrible shape. I encourage you to change them sooner for your safety and the safety of those around you... I know I would never forgive myself if a plane hurt my family.
As for fast charging... as long as the cell is one that can handle fast charging, most new cells do NOT get hot when charging... even from a discharged state. Use reasonable charge rates (1C is the MAXIMUM, so I usually use .5C), you will find the packs do NOT heat unless your charger is missing the peak... then they will get very hot very quickly. I am using a Sirius charger which predicts the peak rather than waits for it... I swear my batteries actually get COOLER on it
, and I also use a Duratrax ICE... it can be set for a what they call zeropeak... it makes the charger very sensitive and stops the charge slightly early... no heating. Stopping a little early is not an issue... my packs are usually large capacity and I check them with a 1 Amp loaded voltmeter before each and every flight... cheap insurance.
That being said... I still give them occasional slow formatting slow charges to help keep the cells equalized within the pack... still necessary to do this. Also... I don't fast charge little 600mAh packs... I don't think the batteries are very robust. Of course... I don't use any packs that small... the smallest I use is an 1100 NiMh... it is very light and has 3 times the current capability of a similar sized NiCd... check 'em out at NOBSBatteries.