Since it's so easy to apply, you can apply after every wash, but it's totally up to you. We don't have any set recommendations, it's really up to the user. You can go apply every month, or go several months without having to re-apply as the water beading and shine will keep going.
Just make sure not to over apply, this product is unlike any others on the market so very little is needed. Only use 1 spray per 2' x 2' section. There are no unnecessary additives such as coloring, fragrances or any other useless fillers, it's very concentrated so if you use too much it may lead to streaks.
Also if you didn't know already, this can be sprayed onto every surface on your vehicle from the paint, glass, plastic trim and rims. There are no limits to it! We've even had customers use it on their kitchen appliances, granite counter tops, even the kitchen sink!