i have personally found gigs of 4 hours or less relativity easy BUT when you have to play 4 or more it gets quite hard not to repeat good tunes what do you guys think?

often the 5 hour gigs dont involve 5 hours of uptempo music, so it doesnt really affect me

average wedding 7-12, background music until 8 or 8 :30, then play a few songs for the kids, then first dance, then after buffet adult dance msuic 9:30 til 12

Don't play all the good tunes at the beginning!
Diversify - look up the big sellers of way back when and today - there's loads of tracks to help carry the night along.

When I first started I used to really worry about filling the time, it seemed really scary. Especially as I thought every song had to be a killer. It doesn't and it isn't. If the crowd is good the time flies in and, going by their reactions and requests, the songs just pick themselves.

And if you are getting a good stream of requests, this can often steer you in a different direction to that which you would normally have taken.

5 hours is a fair amount of time though, and don't look forward to longer events than this very much, although fair to say the early part is more background music, and there is usually time-out for a buffet, so 5 hours can boil down to perhaps 3 - 3.5 hours of actual disco where you are working to get people dancing.

You need to pace the tempo start off with the easy lisning then build the speed / tempo.. When iI was DJing in Magaluf in the 80's I had to do a 7 hour set 6 days a week.. Just try to plan your evenings songs out.

only problem i have is when it's non-stop dancing for over say 4 hours, which isn't very often

Absolutely no issue whatsoever. There are so many fantastic songs that I don't ever feel that I need to ration them- in fact more often the opposite is true. I get frustrated that I can't fit more great songs in.

I don't see how that could ever be a problem. I wish I had more nights like that.