I've had an issue with keeping my wudu for years now due to my stomach (I keep passing wind). However this varies a lot during the day, so sometimes it happens constantly and sometimes not as much. However it usually happens suddenly and I can't control it. So I've always done Wudu once and prayed my prayers as long as I don't break it by anything else (sleep etc). Is this correct?
For example I make wudu for duhr & asr prayers, then I go to work and pray later maghreb & isha (when the sun has set) with the same wudu, even if I might have broken it because of wind?

This is not accepted if you can perform new whudu for maghreb and isha, without passing gas. Therefore, what you need to do is to perform new wudhu for maghreb and isha, and if you passed gas while praying them, no problem.