Blowing bulbs

Hi, I've had my GY-200 for a couple of years and up until recently it had never been used at night. I've just started a new job and I have to commute in the dark and the headlight and rear bulb seems to have a life expectance of about 10 minutes :(
I noticed the indicators flash more quickly at high revs a well so I changed the voltage regulator with one from a breakers but it didn't fix it. I found the ballast resistor under the tank and it reads 430k ohms so I guess it's ok.
Has anyone got any suggestions how to trouble shoot the fault and find out why the bulbs are blowing?

After you changed the voltage regulator the indicators flash was regular at varying rpm?

No, after changing the regulator the indicator flash speed still increased with RPM. Is there a way of checking the resistances etc in the regulator to see if both of mine are faulty?

I'm no expert, but to my knowledge blowing lamps are due to bad earth, but it's not consistent with the other "symptom".

I would make sure the battery is fully charged, then check the voltage going to the battery from the voltage regulator, it could be bad cabling between alternator and regulator causing over voltage.

I checked all the wiring to the lights and couldn't find any problems. I fitted a second LED rear lamp as a back up, and so far I've done 240km without blowing a bulb? Maybe the extra lamp is enough of an extra load to protect the original lights? I'd still be interested if someone has got the figures for checking out the regulator though.