Thanks Bluebird. I am curious at what point you inform your partners or they inform you about another partner coming into the mix. Do you inform them the first time you go on a date or meet someone you have interest in? Or is it only when sex is possible or after sex has happened?
I'll tell you what my husband and I do, and what my girlfriend and her husband do, to give you a spectrum of behaviour.
If my husband's home (he works out of town, gone for days at a time) and I'm going on a date (which I rarely do when he's home, since we have so little time together as it is, but it does happen say over holidays when he's home more), I tell him I'm going out with my gf or for coffee with someone from okc. When I was hanging out with one guy that I thought might become FWB, I talked to my husband about it, and then I didn't mention it when we actually did have sex because he didn't need to know. If my husband's out of town and I go on a date, I probably don't tell him, since we only have so much phone time and there are more interesting things to talk about than random people on the internet (which is all they are to me until we actually meet in person). My husband doesn't date or have sex with other people (not interested) but he loves telling me about women he flirted with.
My girlfriend's husband, on the other hand, has severe anxiety and requires more information to be comfortable. He prefers to know when she's going on a date with someone new, and he prefers to meet them before "naked happens." He prefers to know whenever she's going out with me, and tries to get her to tell him when she'll be home but that's where she draws the line (specifically because if she falls asleep or decides she doesn't want to go home yet, he pretty much freaks out) and she just tells him "probably before work tomorrow." I say "prefers" but it's really more like "insists" in his case. Like I said, he has anxiety and this isn't necessarily healthy behaviour, but it is what it is.
Whether I should expect my partner to tell e when they are spending time with other partners. I don't need to know everything they do or intimate details, but I feel more comfortable knowing they're out with someone else so that I am not expecting them to be in contact with me. This ranges from stopping by the other partner's house or the other partner stopping by my partner's house casually to spending nights together.
Ultimately that's up to you and your partner. You're free to request any information you'd like, and they're free to disclose or keep private whatever information they'd like. Safer sex disclosure is the exception, i.e. you have the right and may expect your partner to disclose if they're having sex with a new partner and whether or not they're using barriers (condoms/dental dams).
Once you're dating someone steadily, it's pretty common to tell a live-in partner if you're going out on a date with them. To me, that's just like telling them I'm going shopping or whatever. Not keeping tabs on everything you do or anything, but just the usual "if something happens, where can I reach you?" kind of thing. Also helps them know if it would be better to wait until you're home to talk.
