My question is pretty simple.
Is it ok to date someone, you are pretty sure you won't end up with?
Are you wasting their time?
does being faithful with someone you don't want to end up with preventing you from finding the person you will end up with?
well if you're young for example you're not likely to 'end up with' them so its ok. on the other hand if one of you are married then no. it depends.
Seems a waste of time to me . . . unless you both feel the same way and just want a bit of fun . . . in my experience though, in any relationship there is usually one person who feels more than the other person and then they end up getting hurt. Could end up quite messy when it does end as I haven't heard of many relationships where 2 people both want fun, start seeing each other, both decide at the same time that they want to move on and then do so happily . . . could be wrong though?
For fun sure! but you may end up falling
You're looking to far ahead. You date to figure out what you want in a partner. if you're looking at each situation as a potential spouse, you're cheating yourself out of a lot of experience.
It depends on where you are in your life. If you're looking to settle down then of course you're wasting your time dating someone who feels "wrong" for you. If you're not looking to get serious, then you should date a wide range of people and get some experience. I dated some very interesting types in my past, people I would NEVER marry, but it was fun at the time.