hi there,
we use the nvm contractor vacs,which in essence are the henry motors, our tub vacs are working every day of the week, get used and abused, on sites, dust, wood shavings, brick dust, chunks of plaster. No problems whatsoever.
each machine is bag checked and replaced weekly, and the silk filters are brushed out.
then for sparkles that are carpetted we use an ensign twin motor upright.
we wouldnt use anything else at the moment, i may look at back pack vacs in the future, but not at the moment, the nvm contactor vacs, work well and are very rugged.
regards
martin