French hinges are not like UK hinges; ours slot on from above, and can be lifted off quite easily.
I don't clean windows too often; this isn't a show house by any means. But occasionally I do take the windows off, sponge them with soapy water, then hose them down to remove all the suds. It's easy, quick, and does the job.
These ones also needed a light 'oiling' with linseed; it preserves the wood and gives it a 'glow'.
The windows were made for us by a local man about 35 years ago, and have lasted very well. We replace bits of missing putty occasionally, but other than that they simply receive a really good cleaning about every five years; whether they need it or not.... More than enough!