Totally in the same boat on this one! We've been married over 25 years and in our mid fifties. Did the exciting intimate mutual exploration of each other in the first few years finding out what was nice, what we both liked. Discovered the excitement of sharing fantasies, fun of sex toys, etc.
Kids came along, career responsibilities broadened, exhaustion and sheer lack of time for each other had its inevitable impact. It's the old familiar story.
The toys are gathering dust at the back of a drawer, the shared fantasies have petered out and energies are not what they were in our twenties (speaking personally, DW is still full of beans!)
We still manage to have sex anything between one and four times a week depending on tiredness and opportunity. And it's good sex. But maybe "bog standard", a bit predictable most of the time. Quite a lot of missionary, woman on top, sometimes from behind. Occasional anal sex is probably the "naughtiest" thing we do. Familiar stuff probably to a lot of middle-aged couples.
We know each other so well. We're both in pretty good shape physically and keep very fit and we still actually fancy the pants off one another, but the sheer familiarity of each other, love each other as we do, etc. etc
I'm reading some great suggestions here, but sex in different rooms just isn't practical when several of our now young adult kids are still living at home. Ditto spending an evening in the bath together, lovely as that would be.
Nights away in hotels definitely a great idea though. Last year we went to a town for our eldest's graduation and arrived mid-afternoon in our hotel room with three hours to kill before we met up for a meal in the evening with our daughter and her boyfriend. An on the spot decision to get naked and jump into bed resulted in the hottest sex session I can remember!! Unfamiliar place, different time of day from usual, spontaneity. It was pretty powerful. It took us both by surprise!
So in some ways yes - things can definitely happen and maybe we do have to make them happen. At same time I wouldn't want to worry too much that "normal run of the mill sex" between a couple who have been together forever isn't a great thing as well, as it definitely is!