This seems to ba another topic with conflicting info.
I have been told that you must travel straight away, as the visa is valid for 24 months, and you need 24 months of living together for ILR.
But the last time I did this, the visa was valid for 24 months from the date of entry into the UK, and you had 6 months from the date of issue to enter the UK, That was in 2002, so it may well have changed