Most leak when driving along when raining as the wind forces the water through wherever it can get. Mine only ever leaked when driving, not while stationary it also had a fold down cover .
In the end it rotted the front area and I had the window removed and all the wood that had rotted replaced . There is not many caravan manufactures that will put front windows in their new caravans because of the leaks.
I would have thought that a large number of caravans (including new ones) have a front window... All three caravans we have owned certainly have, and the Jaycos we have owned have never had problems with leaks.
Our caravans have all been composite walled, so I'm not sure if leaks are more likely in aluminium clad caravans.
I have always inspected seals around windows etc regularly to make sure there are no visible signs that the sealant isn't sticking properly and isn't damaged. I also do the same checks on the rubber seals around windows and doors. If you're particularly worried, perhaps you could try a moisture detector to see if it has been leaking.
Car ones don't open, that is the big difference. Our previous van had a leaky front window, sealing it so it never opened fixed it, but were happy to go without one on our new van.
We have a front window in our Traveller. Talking to a vannner on the Nullabor he likes the front window when Bush camping, so he can see anyone approaching or in the area. Easier with a front kitchen/lounge area.
