Postgresql filtering by value over rolling time period

I am newbie to postgresql and still getting my head around. I have used windows function etc. till date and yes I can make some sense. I have got the following data set: I need to find those customers whose amount > 2 for 4 minutes in a rolling fashion, considering the data for a day. By that I mean in the given data set, customer 1 is one such as it has got amount > 2 at 16:01,16:02,16:03,16:04 and then at 16:02,16:03,16:04, 16:05. If there is any such single occurrence, the customer needs to be selected. Customer 2 doesn't have so. Wondering what's the best approach to do this? Any help will be much appreciated. Regards,