Whenever it tells me it needs updating, unless I'm right in the middle of doing something, in which case it can wait until I'm done. This means a lot of optional things like graphics drivers never get done, but I figure if they're important then I'll find out about it as and when I need to do them. Failed laptops have taught me not to delay Windows updates, but I'm not so motivated as to seek out the ones I won't find out about unless I look for them. Even though I have a very expensive gaming laptop, that's more for the features it has than for gaming.