I would never agree to 90 day payment terms. Most of my commercial customers pay straight away or interim payments on bigger jobs.
I would agree that settling for 60/90 even 120 days of credit,before any argument begins,can be a mistake.
You agree to terms at the beginning,and then live in hope that all parties stick to it.
As for "having" to agree to extended credit terms,due to a companies "policy",i have found this,over a lot of years,to be rubbish.
Companies fail,if they are not able to make prompt,flexible alterations to their business operations. Payment arrangements are NOT statutory,or obligatory.
I have done plenty of work,over the years,for companies who state payment in the time scales above...and been paid on completion of the job,with no issues. This has been,on occasion,for some very prominent companies.
Some have even told me on the first occasion,that it is a "one-off"...and then continued with the same arrangement for the next 15 years!
Having a rolling agreement with a large customer,with whom you have a good,long-standing relationship,can work fine.
Agreeing to 90 days payment,with a new one,can sometimes lead to a great many eggs,in a shaky basket,and the fear of using the word "no".
Saying yes or no to a customer,can be the making or the sinking,of a business,and it is hard to explain this notion,to a keen newcomer,that after all the expense and advertising,turning some work away,can save you more money,than taking it all on.