Caravan rear window leak

My Jayco Freedom also sprang a small leak on the rear window, I spoke to the people where I have booked it in for wheel bearing/brakes etc and they told me it happens often. They said it was caused by the rubber seal around the opening part of the window getting too soft and not touching up at the top. He said the quick fix is to put some canola oil on the window frame ( so the glue won't stick) and then put some silicon on the rubber and close the window til the glue sets. They're going to do mine on Monday as part of the above service and tell me it's that simple and quick that there'll be no charge.
If anyone is interested I'll get more details when I put the van in.
Geoff.