My friend gave up film photography (after trying it for 2 months) last year and I was able to buy a few pro-packs of film and a bunch of developer off of him.
I bought 8 packs of Ilford Microphen. There was no packaging left, only the powder bags, but he claims they were bought in mid 2014.
I checked in the store and noticed that they usually have a one or two year expiration date.
How long beyond that can powder based developers be used?
I got from a friend two boxes of Ilford Perceprol circa 2005 still originally sealed.
Should I try it?
I would like to try fresh Ilford Pan F Plus film with it.
Should I do any reciprocity or development adjustments to compensate for 10-year old developer?
Powder developer will either be good, or it will have deteriorated do to being exposed to moisture.
In the old days, many developers were sold in sealed cans. Unless damaged, those developers are often fully functional many decades later.
Unless the packaging has been compromised, or the Microphen has been stored under very adverse conditions, you should be able to expect a few years of usability before considering discard of unopened packages.
Expiration dates are based on objective factors. But they reflect factors like shop wear and, with respect to powder developers, are as much related to performance of the packaging as the contents.
I recently used a 30+ years old (600cc!) unopened packet of Microphen lying forgotten in the junk drawer to develop several rolls of 35mm film. It worked beautifully.
It will keep for a long time BUT it has to be in good environmental conditions and that often isn't the case.
All depends on the colour of the powder when you open it. If it's still white or close to white its likely fine. If its medium to dark brown then bin it. Light brown is borderline so if you value your negs then bin that too.
I have just used 5L Xtol with Oct 2009 expiration date. Light fog with Neopan 1600 with exp in 2009. No problems whatsoever with Plus-X of the same vintage. Beautiful results with fresh TMY