there are lots of different approaches to temp surfing but the most common one seems to be to begin your shot about 30 seconds after the light comes on. The light should stay on for the whole shot and this has been tested to provide the least variation in temp over the duration of the shot. If you google temp surfing silvia all the gory details will be exposed. ;)
Generally I do get fewer nasty surprises if I stick to this although its certainly possible to get a great shot using other techniques but maybe not as repeatably.
A lot of people, myself included, also prepare milk after the coffee as you dont have to cool silvia down before brewing. (Steaming temp is far too high for brewing)