it depends on which prices you will receive your cards, for example you can buy new @ high price or you can buy used with warranty and discounts
so the less you pay for you hardware , faster you go even and start to receive profits

but my opinion is simple, forget nicehash, in order to receive 25-50% more income from mining you have to lurk for profits yourself
that means find good coin, mine it, and sell it on pumps! with nicehash that is not possible