I just opened up my S1 for the first time and noticed it had been supplied set to "economy" mode - so worth checking this if you happen to have this machine. It's not entirely obvious that this mode is in effect as the heating LEDs for both boilers blink away as if they are working in parallel, but if you look carefully you notice that steam pressure doesn't actually increase until the brew boiler has finished. Well that's my excuse for not noticing this for six months
Does it make a difference to the milk steaming? Yes, depending on how you make the cappuccinos. I start the espresso shot and then steam the milk in parallel, so the espresso doesn't hang around waiting for the milk. Working like this, the brew boiler kicks in towards the end of the shot just as the steam boiler needs to turn on to maintain the steam pressure. In "eco" mode, the steam boiler is unable to turn on until the brew boiler gets back up to temperature, and the steam pressure wanes a bit towards the end of steaming.
Typically, I steam 250ml of cold milk (enough for two capps) using the standard 3 hole tip. It's good enough to get the job done but the spinning towards the end is less vigorous than you might want for good milk texture. Note the S1 Mini has a smaller steam boiler than the S1 to make room for the cold water tank (1.2l vs 2.5l) so the effect of losing heat during the steaming might be more noticeable. You can mitigate this a little by making sure the steam boiler is absolutely full when you start (dispense a little hot water to warm a cup and force a top up of the steam boiler). Or steam the milk before pouring the shot.
Or better still, switch it to "full" mode so the steam boiler can work as it needs to to maintain high steam pressure for the duration of the milk steaming. This also knocks a minute or so off the start-up time from cold (which is about 10 mins).
Phil
P.S. The On/Off switch in the photo needs to be switched if you have the external La Spaziale digital timer option.