Unfortunately it possible to deteriorate due to weather naturally, then perhaps it possible to be broken in ten years later or so. Therefore if there are some replacements it is very useful.
Living in Imported house, living in Japan, preparation is very important to our house.
In generally many of imported house builder doesn't have some stock of replacements, I suppose.
Anyhow Home Made is going to minority way we can not prepare perfectly of replacements, though so we are considering about how to get it anytime you need.
In my opinion, it is likely that domestic (Japanese) standard of windows could be changed or stopped to provide important parts suddenly in ten years or so.
To compare with import sashes, I think it is more kind for customers than the domestic one.
Imports are quite long lusting also the company can stock the replacements for a long time. In fact, I would recommend that you just keep some spare parts for your windows.
In addition some imported windows are available; fiberglass screens which has high durability and more strong than domestic, plastic one in our stock.