We have 8 hours between flights in KL on a Friday night next month. We land at 4pm and plan to go into Petaling St for some quick shopping.
Last time we did this was a Wednesday in December, we got there about 6pm, only to find that many of the stalls had already closed (incl. all dvd stores). I'd only ever heard that Petaling is open daily "till late" - does it close earlier on certain nights or certain times of the year?