I don't really think of it as 'experimenting' or a way to 'practice.' I think that sex and any other type of sexual experiences that occur in the absence of a committed relationship are okay as long as:

--you are staying safe
--you are not doing it just to fill up something that is not there (I did this a lot)
--you are not doing it just for 'practice'
--you and your partner are sober
--you are staying safe
--you are staying safe
--you are staying safe

I think it is okay because in my opinion there is nothing wrong with two people who are attracted to each other having a pleasing experience together. By 'staying safe' I mean both using protection and not putting yourself in any situation which might be dangerous.

My husband and I both have pretty significant sexual histories from before we met each other. When we first began talking about it, each of us was bothered at thinking of the other person with someone else, blah, blah, but in time we got over it. I never think about that stuff anymore.