This may an odd time to bring this up but did you know most Yonex tennis racquets can be strung with a 18×19 string pattern?  Most racquet manufacturers offer an “open” pattern now with Head even offering an “Adaptive String Pattern”, allowing for more than one pattern per racquet,at separate times, of course.

These images are an “old” Yonex racquet but most Yonex racquets can be strung this way.  There is, as far as I am concerned, no compelling reason to use this pattern but I think it is fun to evaluate options.

Why would you want to string any Yonex in a 18×19 pattern instead of their standard and popular 16×19?  I can’t speak for everyone but a reason may be to “firm” up the string bed at lower tensions which can allow more “compliance” and therefore more ball rotation, or “spin”, especially on exaggerated slice shots.

There is not a hard “formula” for string life but typically the more strings filling the head area the longer they last.