It depends on your age and circumstances, as well, though.
I was happily with my, now deceased DH, for 22 years, from a young age. After his death I didn't want a relationship and slept with lots of men, none of which I regret. They weren't taken home when my children were there and no harm was done, it fulfilled a need in me.
That was 7 years ago, I have had a relationship since then, so there is no "risk" from me having numerous sexual partners, or "not making someone my last".
My DH died young from an unexpected cancer, just because you think you are set for life in a relationship, doesn't mean you are and I found my sex drive went through the roof in my 30's.
"Morals" are about how you conduct your day to day life, not how many people you are having sex with, if no-one is harmed etc. I see much more damage done to children when parents think they have to be in relationships and stay in them, because they don't want to be alone, when in essence they are " on their own" they just have the same person asleep next to them every night.