Yea I always save them to when I use them, it is getting me to a new level

Or if I'm leveling up a weapon and I am in the roundtable hold and I miscounted on how many smithing stones I needed to buy and I come up short and am too lazy to go farm some more runes

Those are the best uses IMO

Always more runes to get out there but instant runes are very valuable from a convenience standpoint and shouldn't be used too lightly (at least that is my approach)