998 valve springs and stem seals

[Turboflash]

Putting this out to experienced 998 engine guys -
Soon I'm going to be installing a new SIT kit. My question is how long do the stock OEM valve seals and springs last? While I'm doing this, should I replace both? Engine has approx 350 hours of run time.
I've read that the stock valve springs do not "take a set" over summer while sitting. How long do seals last?
Opinions?

 

[STAIN]

Springs do not usually take a "set" from siting, rather fatigue over time from use. It is the use of the spring that wears it out, not a compressed state.

 

[stgdz]

Those springs will probably outlast the chassis.

 

[Upstater57]

Unless you are building a monster motor for racing, there is no good reason to do this. As mentioned elsewhere, that motor will outlast the sled if maintained properly. The 998 is one of the best motors ever put into a snowmobile. At the end of the season, I put the sled on the stand, change the oil, clean up under the hood, check all the hose connections, pull the clutches, plug in the battery, stabilize the fuel and cover it for the summer.