Btw zeist, i usually do 15-18 sets for chest, depending on my mood and that day's performance. If you want to go heavy, better stick to barbells over dumbbells for the sake of form. I've never had a spotter before so I don't know what good are they for, but from what I see at my gym, many spotters tend to help others lift weights they wouldn't normally be able to lift. And ridiculously some people need spotters even for the Smith machine. I would think that the whole point of spotters is to keep the player safe as well as to keep his form in check, and the whole point of Smith machines is to keep the players safe without the need for spotters. Nowadays I see a lot of spotters at my place who contribute to the lifting of the weights as well, which kinda defeats the purpose of loading on heavier weights.

Also it would be safer to not decide what weights you want to be able to lift by when because that is quite an uncontrollable goal. It will be demotivating and counter-productive if you force yourself to lift weights you can't just because you've set a deadline for it. So yes, you can set a target of that nature, but if you can't hit it in time, its still ok, don't pull your hair out over it. Its no big deal.