Miyot

Where is the horn leaking air? Spit valves, Lead pipe, or lots of places. Seven years doesn't seem long enough to wear out the valves unless you really played a lot or you got the horn used. If the horn is leaking air at the slides, a heavier slide lube could be a quick fix. I read somewhere on this site you could clean your valves with acetone. Being careful not to get this on your felts, plastic, etc. This could help with sticking valves.

If you have red rot and it is limited to the lead pipe you could get that replaced. If you have red rot everywhere, I'd get a new or used horn. A good cleaning and close exam with a light should help with your decision.

Being careful to push the valves straight down, with no lateral or sideways movement could work. I don't know how much replating valves would cost. You could either get the horn repaired or get another one. See,I knew I could help you. Don't listen to me, someone else on this site will surely know more than I.