Its not difficult really, just get something bang in the middle.
SLX 22 or 25 or 27 is spot on really, and if needed get an SLX 18 for everyday pole.
Tell the staff they have to personally take apart each pole for cleaning, spraying re applying tape at least once per month and its part of their job role to look after equipment. If equipment is failing with poles in under a year then you have a problem with staff just abusing and throwing the poles about and not giving a crap.
Our lads make each pole last at least 2 years and even then clamps and sections just look worn at best.