Valve adjust at 15K vs 25K is purely a personal preference. If the factory did a good job, you should be fine waiting for 25K.
However, it's still a gamble that the assembler didn't screw up, or something wasn't seated quite right when they assembled it, causing things to be off by a little.
All things being equal, there shouldn't be much change between new and 25K if everything was done right in the beginning. For most, it's just 'peace of mind'.
I'm guessing the valves would have to be WAY off for you to know they needed adjustment at 15K (without measuring, of course) . Maybe that's just me though.