If I Pause My Slopes Premium Subscription Until Next Season, Will My Data Be There When I Come Back?

If you have a Slopes account all your activities will be kept safe, with or without Slopes Premium. 

(And even better, any recordings you made while you had Premium will continue to have all premium features unlocked for you even if you pause your subscription for a season.)

Just don't forget that the data will be stored in your current account, so make sure that when you come back you use the same account! If you delete it and create a new one all would be lost.