I hate when people claim they're busy and drop out and then I see them starting new RPs. Clearly they're actually NOT as busy as they claimed...

If you're genuinely busy, that's fine but don't lie and say you are when you're just not interested anymore. I'm fine with waiting for posts but people who use being busy as an excuse to drop a RP without even hearing from their partner who would probably be flexible, is a dick move. 

If you're not interested, try to fix the issue with your partner (change the plot, tweak the characters, skip ahead if needed, etc) but don't lie about it and then contradict yourself with other partners. I hate when people drop without fixing the issue. Being bored is natural but I also think it's natural to fix the problem before disappointing a partner. 

Of course, personally if my partner is truly swamped or truly no longer interested, I stress they drop and communicate WHY. The point is, though, lying about dropping is just as bad as dropping without telling your partner. I just hate seeing people who are "busy," doing other stuff with new people. I'm busy but you can also tell my posts are slow. When I make interest checks I stress I am busy and that I'd be picky about any new RPs. Sometimes other people aren't as honest or upfront and it annoys me to no end.