The Company I work for has a contract with JSSI for our TFE-731's. It's spendy, but when we need parts or Tech support, they are "Johny on the Spot".
If a company can be disciplened enough to put away money in a reserve account this arrangement wouldn't be necessary. In the long run, it is however a pretty good plan.
Last summer we had the occasion to replace four FCU's. One went bad right after the other. If we were on our own, Honeywell would not have supported us, in fact their Tech Rep kept saying it was an airframe problem. JSSI kept the parts coming till the engine ran. Guess what? all the FCU's came out of Honeywell. JSSI carried a big enough stick to make them shit the parts.
Later, Honeywell admitted that they had a QC problem at that facility.
Maybe they should stick to making furnace thermostats!