It depends on the tune, Ive been running a set of 555's at 95% for ages and my AFR's are a little on the rich side. I have constant lambda logging so I know its always safe.
One day ill get around to buying bigger injectors and re-tunning it but atm its happy doing what its doing.
When it comes to injector buying time I like to treat each vehicle on its own merit. Id recommend you do the same.