I mean 15 probably generous...
DH and I together since early twenties, now both pushing 40 and two glorious sleep resisting kids and jobs with long hrs and big demands.
Anyway - we used to have a cracking sex life - whole weekends in bed,taking our time, trying new things. I totally understood and expected that as kids came and work got harder that might shift and it did. For quite a while after each birth we barely slept together at all but when we started again I'd mainly describe things as, well...efficient 
. Still loving and all that but mainly, well, shall we say goal oriented and executed as swiftly as possible in the time allowed which given being knackered and limited time was often not long.
Anyway - things v slightly easing up now and occasionally have the time for more than the world's most professional quickie and - genuinely - feel like have forgotten what we did with it!!! Genuinely feeling awkward and weird despite lovely partner I really fancy and have been with for decades....Truly, I think I was a more competent and skilled lover in my late teens...
Anyway - are these just things lost in the fog of kids and life that come back to you or do I need to work things out from scratch all over again?!