You can delay your journey for as long as you like. The only thing to bear in mind is that if you haven't spent over 23 months in the Uk before your spouse visa expires you won't be able to apply for ILR, and instead will have to apply for FLR first and then ILR at a later point (more money).
Assumng they grant you a 27 monh visa you won't have this problem unless you delay your journey for more than 4 months.
