My friend from work has had three patches on an old tire & one plug on his newer tire(both rears).The plug is recent(within 2 weeks), but the patches are from a year to 3 months ago.Rides to work everyday & has never had any problems.Wore out the old rear tire, got a new one about 3 months ago & now has a plug on the new tire.So far so good.Ive used plugs about a half dozen times on my car with no problems, but have yet to need one on my bike.