@Tim2050 each host is different when it comes to how far ahead they open up dates and accept bookings. I'm sure there are many homes that still have yet to become available . But if you've already found somewhere appealing at a good price, i see no reason not to go ahead and book it!
My caution would be: when booking far in advance, be sure to check that the host has an established track record with no host cancellations. You don't want to risk being cancelled on after the best options are sold out.