Hmmm, I asked my manufacturer about pulsing the LEDs, and they replied :-
Hi John,
I see . It's ok with leds . We did pulse testing on such leds.
But it will increase the decay of light a little bit .
You can try an samples .
So I asked what pulse width and frequency they tested at ? they said :-
Frequency is 1.0hz .
1 time per second. We tested 3 monthes . And if leds ok . then we use the chips.
which I work out to being on all the time 
so I asked if I can pulse them 150mA at 10% M/S ratio, and they replied :-
Hi John,
No . 30mA is the max current .
150mA will burn the leds.
If need 150mA . You should use 0.5W
So it looks like I am abandoning multiplexing for now as I have a couple of thousand of these LEDs left, even though I can't get specs on them