how long before you give up

Kara • Married 🇨🇦 SAHM Girl 09/09/16 -x- Boy 08/29/19 Waiting to TTC #3

How long do you try to put your toddler down for a nap before you give up and go with an early bed time? I am a huge routine fan but sometimes it takes a really long time to get her down (21 months old). If she won't nap I get really stressed but I want to be more "go with the flow"