For example, if they are ejaculated on clothing, or toilet seat etc. Do they lose motility(ability to swim) and just stay in the ejaculation? I tend to masturbate a lot and feel guilty and paranoid about leaving fluid behind.

No, they leave the ejaculate and find a host... No, just kidding. Just wipe it up then and put it in the toilet and flush. Your male body is always producing sperm, so you will never have to worry about it being wasted on clothing, toilet seat, or whatever you are playing around.

Good grief... what else are you "leaving around" too.

Ok, besides just being gross, you need to clean up after you do it. Sanitation is a real issue, if you leave it everywhere.