We haven't got a double pram and no intentions of buying one. DD1 was 2yrs 9months when DD2 came along. I either carry DD2 (have a sling and a more structured carried) and have DD1 in the single pram or have DD2 in the single pram and DD1 walks.
This is pretty much me, with a 2 year 3 month age gap.
With the exception that I have bought a cheapy second hand double that I only use for long walks (walks between 3 and 6 kms) but never any other time. If you don't do the longer walks then 2 without a double pram is achievable.