I worked on a Tanning Salon back in 1990 thru 94, first to install a branch circuit for a new "Stand-Up" unit, then over time upgrading the service, extending into another suite, hooking up normal "Lay-In" units and one "Hi-Intensity" unit (uses HID lamps instead of VHO Beryllium Fluorescent lamps), installing timer circuitry + controlls and a bunch of other things.
This Client specified running the units at a slightly higher than specified voltage, which would result in a better tan with lower UVA / UVB / UVC risks. Lamp age was reduced from the boost, so lamp maintenance was done much sooner and more frequently.
I installed quite a few boost transformers at this place!
For the few years I worked for that client, only 1 ballast needed replacement - which was on an older unit. Lamps operated fine - and output over time didn't have a drammatic loss or change (measured with both a normal light meter and UV meter).
Lamp ends became darkened as would normally, but cathodes did not fail.
Lamp holders remained unscorched too! (mainly due to upgrading all lamp holders with new higher quality ones when a new machine arrived and / or upgrades to existing older units).
Might have been just "good luck", but there was never any "Issues"
Was not only a fun set of projects (different things to do and also the customers
...), but I sure learned a bunch of lighting related stuff (needed to dive into personal studies to properly specify, install and understand these machines).
Just my $0.02