I'm sure that bottle will be fine for the working solution, as long as you keep it full.
For your bottle of replenisher, I recommend the following:
Since Xtol comes in 5l kits, you will have a lot of stock developer when you mix a new kit.
Oxygen is harmful to developers, so you want to eliminate as much of it in the storage container as possible.
My solution is to store the stock Xtol in 1l bottles, completely full, and then I have one 2l collapsible bottle, which allows me to evacuate all the air in that bottle as I use the replenisher, before I seal it up again for next time. When you start to run low in the collapsible bottle, you pour in another liter, until you run out of full 1l bottles, and that's when I mix a new 5l Xtol kit and fill them up again. I have run my Xtol batch since July 2009, and I have just kept on replenishing perpetually since.
One thing you will notice is that after a while some debris will start to form in the working solution. It sinks to the bottom of the container, so it isn't really a problem. Use a working solution that is slightly more than the maximum amount of developer you will ever need. The largest volume I ever need is 1,750ml, so I keep a 2l working solution.
Some people filter out the debris. I will sometimes completely empty the storage bottle, pour in some hot water and some carefully washed pea gravel, and shake it up pretty good. This clears most of the debris that's stuck to the bottle inside walls, and comes out as I pour the pea gravel back out.
When I pour back the developer, I leave about 200ml that's on the bottom of the graduate, and just pour in fresh developer to fill the tank up. It's tough to over-replenish Xtol anyway, so it doesn't make much difference.
- Thomas