Double stroller for 4 year age gap?

Amanda
Has anyone with 3-4 years between kids found they really needed a double stroller???
My 3.5 year old is petite, and with her short legs, gets tired walking really easily. I'm trying to avoid needing a double stroller. When this baby come in late January, she'll be less than a month away from turning 4. 
A friend is going to give me for citi mini glider board to use with our single citi mini. And I hope between that, and wearing the baby and putting the 4 year old in the stroller sometimes we'll be good, but I see people selling used double citi minis and I get really tempted.... Any advice for this age difference??