Might anyone have any feedback on the general lifespan of Incoe batteries ?
I know of course that the lifespan of batteries can be quite subjective, but
just wanted an idea.

I've been using mine for exactly one and a half years and was wondering
how much longer it might last. I have an NS60-L, non-maintenace free, in a
Proton Iswara 1.3. Hoping to use it as long as I can, as batteries don't come
cheap these days.

I remember reading one of the Filipino car forums and one guy said his
standard non-MF Incoe NS60 was still going strong after four years !

Incoe is supposed to be a Japanese brand, made in Indonesia. I think their
NS60 have 11 plates, but some say only 9.

Mine still starts fairly strong in the mornings, and doesn't need much of a
topping up, maybe 5 mm per cell a month.

Nice info bro, but Incoe is not common in Malaysia market ya. I was actually also looking for this brand but cannot find yet who's selling them.

FOUR YEARS is an extremely long lifespan for a battery these days,
moreover maintenance free, which usually lasts shorter than normal types.
MF batteries typically lasts about two years, two and a half at most.

I've just changed over to a normal Incoe NS60L a few weeks ago.

Bought at AME Auto at Sea Park for $ 170. Batteries don't come cheap
these days.

Trickle charge  ?

You mean you bought an electronic battery charger to use at home.