will flowering take longer with mh?

hi,i am in to week 8 of flowering with a 250 mh,i am growing white rhino,i have learnt that they should flower for between 8 and 10 weeks.will it take longer cause i using mh and not hps.i only have 2 plants and the yield looks to be small,but this is a first grow and i will change lots for my next.

hps would help a fair amount during flowering becuase it gives a more orange light of the spectrum which simulates the autumn sun when the plant knows its time to flower. and its said that hps increases your yeild.

i know that hps would be best for flower,i thought i was using hps until week 6 of flower when my bulb died.i went down local grow shop and the guy told me it was mh.i have tried a hps bulb in my lamp,but its an old one and will only run mh.what i need to know is will it take longer to flower.or will it be the same as with hps,just with a smaller yield.thanks