Optimate 3 charger / battery, possible issue?

I was wondering if any one could help with this small problem, a friend of mine has an optimate3 charger plugged into his bike when it is not in use, however recently the charger has been showing differant readings, sometimes it stays charging all the time (it should charge for two hours after being plugged in) other times it shows that the battery is weak other times that the battery is good then it sometimes just stays on desulfate. The battery itself shows no sign of being flat as it starts  his bike with no trouble at all and it runs all the electrics fine. I was wondering if these chargers have a life then fail to work properly after a time, he has used it for about eight years with no problem up to now. Any input on this would be very welcome.

If I recall Mr I had a similar issue to this but I can't find a post on it so it may be that we discussed it in person. I think that battery is just starting to go down

You are correct Crash I have had this very same issue.
I keep 3 separate motorcycles plus several spare car and motorcycle batteries topped up by using 2 chargers and have had this issue twice over the last few years. For me it was definitely the battery both times and I know this firstly because I would randomly swap the battery optimisers and would get the same resulting issues with just those 2 batteries. From my own experience what I did notice over time was how quickly they would discharge when under load compared to a properly 100% healthy battery. One of the batteries was even put on a dedicated desulphater by Doc Cox but this was not a long term fix.
So from experience I would guess that the battery is just starting to show the first signs of degeneration but with that said it probably has a lot of serviceable life left in it yet.

Thanks both of you for your comments, I'll advice him to keep an eye on the battery.

One other thing with these so called "sealed maintenance free batteries" is that they are lying!
What the actually mean is: you are too stupid to maintain this product and we don't want you too either because then you will throw it away when it shows signs of trouble.
Firstly they are no more maintenance free now than they ever were, they only difference in this one and the one you bought 20 years ago is that they have written maintenance free on it.
These batteries will evaporate the fluid in the cells through the tiny breather hole in just the same as your old batteries did. So it would be worth popping off the long cap on top of the battery and checking the fluid levels. Just pop the cap up with a small flat screwdriver or similar but obviously be as careful doing that as you would with any other battery due to the acid.

It is a great marketing move to write maintenance free and expect people to buy new.
Good to know they can be refreshed

I have passed on all comments, thanks again for your answers.