Developer Shelf life

I've only gotten back into the dark room for less than a month now.
I'm keeping it pretty simple for chemistry to get re-started but I've got a question on the shelf life of the developers I'm using. So far I've stuck with Ilford Ifosol 3 for film and Ilford Multigrade for paper.
I have nothing that is more than a month old since purchase.
When I've gotten down to the last 50-60ml of both developers It is turning a dark brown in the original bottle. This has happened with 1 bottle of mulitgrade and 1 bottle of ilfosol 3. I dumped it and opened a fresh bottle. I guess my question is- Is the color change indicative of the developer having gone bad or would it be OK to use once mixed to the proper dilution.

Developers vary considerably in their longevity. Some developers can suffer "sudden death" where they will lose activity almost overnight. Some developers such as the original Agfa Rodinal will last literally decades, even in half used bottles. If there is any concern about the likely life of a new-to-you developer, I would suggest decanting fresh stock into smaller bottles.

It varies a lot. The brown color is caused by developer oxidation products, which accumulate as the developer becomes exhausted. But the degree of exhaustion versus the color is not regular and can not be used as a reliable indication. Some developers become exhausted before any brown appears. But the original Agfa Rodinal stock solution was dark brown, and it lasted almost forever in its sealed little vials. Amidol developers, which last only a few hours anyway, usually become quite brown about half way through their useful life. Dektol is useless when it becomes yellow. Anything beyond a light tan usually means HC-110 stock is no longer reliable.

Developer exhaustion usually happens by oxidation of the developing agents. That happens in a lot of ways. First is the oxidation that occurs when developing - the normal developing action. Next comes oxidation from air in contact with the solution, either in the bottle or in a tray or tank. Then there is oxidation (and other chemical reactions) from contamination. This is subtle. The chemicals used to make solutions are not absolutely pure, and some of the impurities may affect the developer (either slowly or rapidly). The same thing goes for the water. Contaminants, both chemical and bacterial, can also enter from the air. Except for exhaustion through use, these are usually unpredictable for the small darkroom.

You really want your darkroom solutions to be reliable so that they give repeatable results - so you can follow the same routine and get comparable results every time. Developers do not die all at once. As they become exhausted, they first begin to act more slowly. This often happens long before any color change appears. As they become weaker, they also develop photographic materials differently, changing the curve and often increasing fog and maybe stains. You want to avoid this for consistent results. Large laboratories use replenishers to compensate; most small users simply replace their solutions often. Most manufacturers list capacities and working lives for their products. Pay strict attention to these; treat them as absolute maxima and generally replace solutions well before their end of life. One shot developers for film help a lot, but pay attention to the shelf life of the opened stock solution.

When Ilfosol 3 turns brown it should be thrown away. Specifically for Ilfosol 3 brown color means bad developer. The shelf life of a half open Ilfosol 3 bottle is 6 months. It can be stretched to 8 months, but not longer.

Thanks guys. Looks like the shelf life of 50ml of Ifosol 3 in the tightly capped bottle is less than 3 weeks.
I think the obvious solution to this problem is that need to use it up faster.

I recently used up the final 50 ml of some Multigrade that had turned brown. Definitely slower than fresh, but it worked fine. I threw out the solution earlier in the print session.

With print developer, if your developer is shot, you waste a test strip or two before realizing that it needs to be replaced - not a great risk if you want to try using it.

With film developer, it is much more risky.

I wouldn't have tossed the print developer.

In general, it can help to decant to smaller bottles earlier in the process.

There certainly are other film developers worth considering. Something like Kodak HC-110 (which I use) or D76/ID-11, which is sufficiently inexpensive to make throwing a portion away less painful.

Or my favourite recommendation - X-Tol in a replenishment regime.