You can only straighten a stick if its seasoned, otherwise it will revert to its natural state in time. And if seasoned it will stay straight after the process.If its oiled regularly it should last a lifetime
if you use a stick that has a dogleg in it , its not safe for the purpose it was intended for.and would not give the support for the person it was intended for .
Although people don't put there full weight on a stick those that need a stick for walking and use it for a lot for carrying there weight need a straight and a slightly flexible stick for safety
A commercial stick maker would never use a bent stick for this reason.
I know that a lot of American stick makers say that it gives a stick character if it bent ,but these should be used for decorative purposes and not as a walking aid.
English stick makers take a different approach and wouldn't use a stick that they couldn't straighten or has a dog leg in it., particularly if it was a competition or for a walking aid.
I personally wouldn't use a bent stick and discard any I cant straighten. And you cant straighten a stick if there's a knot where its bent
The majority of sticks used here are around 1 inch in diameter anything larger than say 1.5 inches anything larger than that I would consider clumsy to use and to heavy depending on the wood used. I don't use anything over 1.25inches diameter
I harvest my stick myself mostly hazel they grow reasonable straight and considered to amongst the best for a walking / hiking sticks.these are usually seasoned for 2 years
You take a different approach in the States and a lot boils down to personnel taste