While you can still opt to repay your loan on your next payday, it is far more common these days to take them over a period of 3 months or more. Spreading the repayments over a slightly longer period has been a natural evolution in the payday loan market, making them much more affordable rather than having to pay a large lump sum out of your next pay packet.
Ultimately, the decision on repayment terms is yours to make. If you want to borrow just a small amount, then repaying on your next payday may make sense, whereas a larger sum would be more manageable over a longer term.