Generally, you want the weight to be light enough to keep a good pace on your first three reps. Then you wait a breath and do the fourth rep. Finally, you take two breaths of pause and then do the fifth rep, which will be the hardest rep, but shouldn't take seventeen seconds to complete. These are guidelines for submaximal volume sets and usually apply more to the first and second sets rather than all of them.
On the LP programme where you're doing only three sets, usually at your perceived maximum each day, it can be hard to maintain this. You shouldn't only progress in weight so long as you can keep this pace going, but you shouldn't take two minutes to complete one set. Once you're at this point of doing very lengthy sets, you may want to review your training and recovery "logs" (bracketed for the latter word) as a significant retardation in bar speed implies a harder time recovering. This isn't always true, though; really heavy weights will never move as quickly as light weights, especially on volume sets.
The experienced eyes have it, in that there's no hard and fast rules. But try to keep it smooth and on pace. Don't rush your reps or sets, but don't turn it into a leisurely stroll either. I find the above helps for sets of five as sets of three usually don't allow one to do all three reps in the span of five to ten seconds, which is completely feasible on a set of five.