My experience.
When Lucky died and left his partner of 20 years I had 5 Tiels left ans still do.
I tried to match him up with another Tiel.
The two girls don’t like Baby, they hiss and beak jab at him.
He does get along somewhat with either Popeye or Cheeky.
Cheeky when in Baby’s cage , they get along for a while but eventually Cheeky start chasing Baby around the cage and forcing him away from his favorite perching locations.
Baby is 22 years old, quite old for a Tiel.
I think it’s better he be relaxed in his old age.
Popeye…..
Popeye is psychotic or anti-social.
He appears to get along with Baby but I fear he could snap and decide Baby is the anti Christ.
My point is Baby has been around these other birds for many years but that doesn’t mean they get along.
Baby went into a serious funk after lucky died.
I would say it took more than 6 months but less than a year for him to regain his…….. interest in play and a desire to continue on.