No it's true for any Shinobi that keeps TRAINING in to old age. There are several old characters in naruto that displayed skill in physical abilities despite there old age.

The eternal gennin side character is a perfect example. He went to the academy with the third hokaga. Obviously not as skilled in chakra control as the third but still phisicaly capable.

Only non-Shinobi are effected by age the way you suggest.

You guys don't get it!!!
Yes there physical energys are less then a healthy adults when you reach old age.

But there abuility to use that energy effectively is through the roof. However they can't replenish there physical energy as many times as they used to(I.e stamina) and there for can't sustain combat for long periods of time.

So in essence there chakra in regards to its power and effectiveness dose not decrease!!!
But there Stamina dose. And sence chakra relays on stamina for the energy to make chakra. It can be said that the total amount of chakra is decreased but only alittle because there skill in using that energy to make chakra counter  balances any energy lose do to old age.

And I dare say that some are so skilled at chakra control like tsunade that they actually have more chakra in old age then they did when they were younger.

Why didn't you just wait until it is done to post it?

noted
hope you'd update the character lore and stuff soon.
Stay active and have fun ^^