I haven't ever mined so actually I don't know much about that. If I were mining though I'd probably just hold other than maybe selling a proportion of the generated ETH regularly just in order to pay for the electricity costs if i needed to....because this should work out like a dollar-cost-averaging strategy (I guess) which many people recommend.

Of course, it really depends if you think ETH will be worth more than it is now when they eventually switch to proof of stake. You'll have to decide that yourself. I think it could well be worth more at that time, but that's just my guess.

Personally though as I have a reasonably substantial amount of funds, I don't like to leave it all in crypto, because of the downturns. This means trying to sell the tops and then buying back in at the bottoms with at least a good proportion of my holdings.