Have used the old 5955's for flaps forever with success, as well as lately using the spektrum AR6030's.. so far so good.
I think its so very important to monitor the overall or servo current during setup so that you are not loading the servo at flaps up and it heats up, then when its needed its already hot.. Servos on direct lipos that have a higher voltage can produce more wattage load in general, and can heat faster if loaded..
When I help set up guys planes, most often, if there is any binding its usually the gear or flap servos.. One time, we found a gear servo loaded at 2 amps..it chewed thru an A123 in short order.. If we had not put an ammeter on it, it would have run the battery out on second flight.
also in General: Most a/c should never have more than 1 amp of load on them sitting on the bench.. I get usually somewhere between .25 and 1 amp depending on how electronic crap is in the plane..