It's a question of what your after really, some games have very little sexual content and end up being good, making you earn the pay off and making it feel more satisfying by doing so, others use it as a way to bait their patrons into staying around and just end up blue balling the player over and over, it's not solely about volume of sexual content or how regularly that content is delivered.
IMO you need to manage the rate at which sex scenes occur, the time it takes to get to them, the size and depth of those scenes, you could call it "sex density" of a game, how much of the game is sex compared to build up and gameplay ect. I've played games that have a very high sex density from the first update and they often end up being too reliant on the sex scenes and not really doing as much as they could with the story, however if you end up front loading the story and end loading the sex content too much then the sex will be too dense at the end and become monotonous, which sucks after such a long build up.
I think in part this is because a lot of devs don't use/understand the "act" structure of films, books and plays, they don't realise that you can put a little in in the beginning then not be obliged to drop sex content every update from then on, in many cases devs seem to feel like they can never release an update with less sex content than the last since that is considered the "good stuff" when, especially in a VN a sex scene without context and build up is less involving to the player in most cases.
As to the actual question of the thread, no, it shouldn't say "no sex content" tag, that would encourage the dev to front load the sex to ovoid this tag and make it less satisfying, however a "sex content pending" tag may be useful though it may also have the previously mentioned undesirable effect.
