Hi,
It's normal. ini files parsing is done by PHP's internal C code, so it should be lightning fast, unless your translation override file is hundreds of MBs in size. So it mainly depends on the number of products you have. If you have hundred of thousands of products and each one has long translation overrides, it's likely it would become slow so reducing the size of the translation keys will be good.
For a few hundred products shop, it shouldn't change anything.
I would personally still try to have small translation keys just to have something clean, but it's more of a personal preference than anything else.
What you can do is to have only a translation key in the main description and then enter the description for all your languages, including your main language.
That way, you can decide what you want the translation key should be for the translations.