Carbs and petcock mess after sitting for 3 months

[MrJoel]

Guys, it is common for seals and o-rings to dry out after a few months of non use? I've had the tank off and being redone which has taken much longer than expected and I switched my carbs over from my running bike to the project bike. Well, finally, I have a weekend to start putting everything back on the project bike and it looks like a sprinkler going off under the tank. The petcock was leaking at the face of the selection knob so I switch it it out with another one I had sitting around...same thing! Then I put in a smaller $8 vacuum petcock that fits (and works) and turn it over...after about 20 seconds it hits a few times and I wait a minute (about 1/2 gallon of gas in but elevated tank and on prime...hit it again and she starts running kinda loppy... Then I notice gas dripping down off the bottom left of the float bowls...then it starts pouring down... I can't see much due to the lighting but I think it's from the seals between the carb fuel lines. They were new a year ago and not leaking when I stopped riding the bike back in April/may... Will they swell back up or is something else going on? Suggestion???