Just to comment on the “icing at high altitudes” part. Icing doesn’t always or only happen at high altitude. It’s more dependant on where the freezing level is at, generally speaking.
A MPA would “climb thru” the FL on the transit to their op area at high altitude. As it gets close, it will decend to a lower altitude to do things like drop sono’s, RADAR search, do the S part of SAR, etc. sometimes it might stay below the FL, or climb thru/decent back thru the FL multiple times to reposition, maintain RF coverage, conducts comms, etc.
Icing can happen fast and accumulate quickly and shedding it uses energy. Some de-icing can be done with things like engine bleed air, some is done with electrical power. Generating that power burns fuel. Ice creates drag and weight which requires more power which burns more fuel.
Any amount of time you can use On Station is valuable, whether it’s prosecuting a submerged contact, SAR, ISR, etc.
Icing is never going to increase your ONSTA time.
* sorry if that is a bit “Capt Obvious”; I just figure many folks aren’t familiar with LRP flying.