Problem with these products with low usage is that the HDPE bottles where they come, with not perfectly airtight caps, cannot be squeezed well. Using inert gas, heavier than air (eg. butane) will solve the problem.
But, we at our club have never had any problems even with 6 - 9 month old undiluted solutions, even without any inert gas. On the other hand, there are many cases where XTOL has gone totally bad in 4 to 6 months, even when the most of the air is squeezed out---C-41 chemicals don't seem to be this strict.