lighting myths and sales pitches

I sell and repair gear,[declaration of interest]and I see on a weekly basis people being sold stuff they don't need or can't use and I would like to start off a thread of things to look out for.One big sales pitch which can cost thousands of dollars is the DMX sale.A DMX dimmer is in fact an analogue dimmer with a DMX decoder built in,DMX is not a type of dimmer ,it is a system of transferring data.So should you buy new dimmers?.Dimmers are like cars, there are good models and bad ones, unfortunately it usually takes a few years to find out.If you have good reliable analogue dimmers then buy a demux for $400 and keep the dimmers as new DMX units are going to cost $2000 per 12 way.The old Strand JTM and Minipack dimmers were particularly reliable.On the subject of desks, DMX desks are now so cheap they can be considered a consumable with a 24 way memory desk at $400 and a 48 way atb $660.Incidently no one has mentioned that Strand UK has gone broke and will not be selling or servicing gear any more.Another sales con is the RGB floods with a dmx controller,not only are they overpriced but highly inefficient as 80% of the light is lost in the filters and as you dim down the blue, the colour temperature of the lamp reduces so there is no blue content to dim.Finally a word on the quaint practice of pre-heating lamps, I recently got into heated discussion on this practice which lead me to do some experiments which proved that preheating lamps had virtually no effect after 4-5 mins and absolutely no effect after 25 minutes, so if you preheat your rig you can save time, power and lamplife by discontinuing this practice.Ilook forward to other feedback in this area.