How many bundles you can purchase from hb

Not sure of the exact time, but that's also a limit per payment method. You can double that by paying both via PayPal and credit/debit if you don't want to or can't wait (e.g. wanting to buy gifts shortly before a bundle ends).

i think once you bought the 3 bundles, this lasts for a few days. maybe a week. not sure.

Never happened to me so I'm not sure about it :P

As many as you want, as long you have different sources to pay with ...

Regularly with one payment source only: 3 max, sometimes 4 for no reason,
and sometimes only 1 likely because you have purchases made recently (for other hb bundles).

Two bundles per payment method.

I think that's stupid. If you are paying for it, why not buy as much as you want?