I have a 3 hour doubles date Saturday and I know there will be lots of various things going on between rounds. im thinking it would be a good idea to keep a condom on the whole time to be sure nothing slips in where it isn't supposed to. also so the ladies don't think I am trying to do anything not allowed.  

Otherwise I think you ought to lay in a supply.  No harm in covering up early & often.

whether you cum or not.  If they agree to use FM condoms, you don't have to.  Discuss it with them.

just to take a break.  Sometimes the condom irritates my cock.  Sometimes I want more BBBJ at that time.  Of course I always don a new one when we resume the FS activities, but I've never had a lady question my desire to get undressed partway thru.

Most women, unless you are with two ladies who are an actual "couple" are going to insist you change condoms each and every time you change vaginas, if you have ever had a really decadent, debaucherous,  multi hours threesome, you'd be amazed at just how many condoms you can go through.