I've done a few extractions now and was wondering that rather than start again when the pulls get weaker, can you simply add another say 100g of MHRB if you have enough space in your jar ?

If you've done a few extractions now as you say you should realize that the answer would be no !

..i don't see why you would want to.

whats wrong with starting another extraction? or doing a larger extraction (imo: when doing large extractions, its best to break it into a couple portions for pulling anyways)

Thanks guys.

I thought it may just make the process slightly simpler and the MHRB that is present might continue to release more spice over time ?

It still will release all it's got to give just keep pulling till it gives no more !!