Unless employers suddenly start handing out extra months worth vacations, an extra family trip sounds unlikely, let alone 10.
Maybe I'm unusual but I rarely have any plans further than a couple of months ahead. Whether I'll be going on any long trips in the next 12 months isn't something I have any idea about yet. It depends on loads of factors (money, weather, work, whether I can pick up a bargain, etc.)
A month or two in advance is just fine, most people can do as much. They do know how many days of vacation they get though, and it's unlikely to change, so any plan you have you keep.