How old is too old to pop for gender?

Just like the title says, how old would you guys say is too old to pop a snake for gender as oppose to probing? My red tail is close to 6 months old now, and I dont want to potentially injure it if too much time has passed. Thanks.

Well the older they get, it becomes harder to pop, probing is your best bet.

Boas can be somewhat hard to pop as is, better off having someone probe him/her.

Thanks guys.