Floyd: You may not be aware that the manual you have accessed is pirated, proprietary intellectual property (as are most of the manuals provided at such places).
The manuals are not pirated. Lets stick to facts and avoid fabrications.
I typically buy manuals from www.2manual.com
, but the previously listed source is just as legitimate. Epson like other companies makes their manuals available for purchase by service technicians.
That aside, your statement says "any Epson printer" but that's not really true. There are various models with various power regimes and there are many people using printers as old as, say, the Epson Stylus Pro 7600. There are also other models being used now for photography that do not use aqueous based inks and the Epson models (to keep it related) certainly have different requirements and processes.
Wonderful, but just find an Epson InkJet that doesn't do what was described with respect to Standby and Power Off modes. The 7600, for example, does exactly as described (see page 116 of the Service Manual). The reason is very simple too: it's the only thing that makes sense. And of course that relates to InkJet technology, while other types will do whatever is equally appropriate.
In regard to the comments from HP, they relate to HP technology which is significantly different to the micro peizo technology employed by Epson. I would not necessarily relate the two in terms of preferred practice.
Specifically for the 4900, the manufacturer clearly sees value in powering the printer down and finds it to be more than any downside in so doing (hint: there's no downside) and has implemented a default state in which this happens after 15 minutes of non-use.
It goes into Low Power Mode, just as I have described. Power Off is different.
Actually the 4900 has a configurable time to Low Power Mode, with 5 steps from 5 to 180 minutes selectable and 15 minutes is the default. More telling though, is that there is indeed a timer to go to Power Off. It is selectable in hours from 1 to 24, but apparantly Espon doesn't "clearly sees value in powering the printer down" because by default the timer is disabled.
Taking into consideration my extensive personal experience with these printers and discussions with people who genuinely know what they're talking about (far above my level), my recommendation is to switch off once you have decided that you are finished for the day.
Discussions with people who have and read Epson Service Manuals, for example?
The printer will not unduly wear or have any impact whatsoever on the MTBF or total expected life as a result of the additional switching off and on, but it does initiate some important processes such as writing data to the ink cartridge and maintenance tank chips, updating internal NVRAM data, performing AID checks and time/usage-based cleaning cycles, just to name a few. These are not critical in the sense that the printer will fail if you do not do it, but you run the risk that an interuption to power or otherwise of the operation of the printer may result in these processes failing which can (and I have seen numerous cases whre it has) cause issues.
Those are done either when entering Standby Mode, Low Power Mode, or are totally superflous unless power is actually removed.
The key point is your first sentence, "will not [...] have any impact whatever". That's a two way street, there is no harm to turning it off but there is no harm to leaving it on.
The downsides to leaving the printer on are limited and most people who do so will never encounter them, particularly if they use a UPS (see above) and so there is no need to criticise this practice if it suits a particular user. However, the best practice for a 4900 would be, in my considered opinion, to switch off when you believe you have finished printing for the day but not between print sessions within a given day. This will achieve the best balance of all the various factors at play for most casual users (which is most users, even proffesionals).
I don't agree with which is "best practice". There is no harm done, but there is simply nothing gained by going through a power on/off cycle every day. It's also a waste of ink.