Is it possible it's JUST the battery?

MY 2007 has just over 5000 km on it. Washed the bike the other day, then parked it over the weekend in my garage. Monday morning, put my gear on to go to work, and couldn't start the bike. Turned over for a few seconds before the juice ran out. Put my ctek charger on the bike, and got the keys to the car. My commute to work is about 17 km, and I never plug the bike (charger) in during the summer months, even with an tracking alarm on the bike.

After work, the charger reported a full battery, so I disconnected it and fired the bike up. Seemed to start instantly with no cranking (like 1/2 a rev and it was running). Noticed that the headlight beam shining on the garage wall seemed to get a little dimmer when I revved up a bit. Uh oh...

I shut the bike off, and test the battery through my remote charging lead - 12.7 volts +-. Start the bike - 13.5 - 14.0+- depending on revs, but the light still got dimmer when revving the engine, even while the volt meter was reading 14+- volts. I notice that the time is wrong on the clock again...

I've read a lot on this site saying to get a new regulator/rectifier, but it seems to be doing its job with respect to keeping the voltage from spiking much over 14.
For any other motor vehicle I've owned in 50+ years, I'd just put another battery in it, but the number of posts seem to dictate that the regulators are prone to failure. I'd rather avoid the expense of a regulator if not required, but seeing the headlight dim when revving the bike while the battery is showing 14 volts has me wondering...

Any advice is appreciated.

I've always replaced both battery and reg/rec at the same time on my 996S and SDR, just in case - can't be proven to be necessary, of course, but I'm convinced bad battery buggers reg/rec and vice versa - current battery and reg/rec on the SDR have lasted 40k+ miles.

Rec/reg shouldn't really be going at 5k km even if it is 6 years old. I'd expect to see spikes over 14v if there was something wrong with it. Mine went to nearly 19 when it went.

Thanks gents. I'll spend some more time with the meter, but I'm thinking the battery at 5 years is done, and the rec/reg is OK. Of course replacing the rectifier can't hurt (just my wallet).

Check all your connections - especially on the battery and starter relay.
I thought my reg/rec was playing up - bike cutting out and wouldn't start etc but found that the connections on the starter relay were loose.
Hope its nothing major

I had a little more time with the meter today.

Battery with bike off is 12.66 volts.
Battery shows 12.12 to 12.15± volts with the ignition and lights on, but bike not running. (Alarm and autotune preheating providing additional drain).
At idle (1800 - 2000 rpm) I get 14.2 volts (Canadian bike, so headlight is ON - can't be switched off).
At 3,000 rpm, voltage drops to 13.55 and 13.45 volts @ 6000 rpm.

This should be sufficient to charge the battery while riding, correct? (or am I missing something).