How often a baby wants to feed depends on his personality, how hungry and thirsty he is, how tired he is, and whether or not he is well and happy.
In other words, there may be some specific reason why your baby sometimes or always wants frequent feeds or he may just be asking for what is perfectly normal and desirable for him. If you are tired and feel that it's because baby is feeding so often, then relax. It's normal for new mums to feel tired. Your body is still trying to get over the birth and this naturally takes time. At least when you're breastfeeding, you're sitting down and relaxing instead of running around doing housework.
Check whether you're making enough milk, and if not, increase your milk supply. Lots of babies want to feed very frequently at one particular time of the day, generally the evening, and cry if you don't feed them. If he is healthy, thriving and gaining weight, he may simply have got into the habit of feeding frequently. If you are not happy to go along with this, you may be able gradually to lengthen the gaps between feeds by distracting him with various activities or by asking someone else to look after him when he might otherwise be likely to want a feed.
A good tip is to get him used to larger feeds. Try expressing some milk in the morning which is when most women have most milk. Keep this milk in the fridge, and when your baby starts wanting frequent feeds - perhaps in the evening - give it to him from a cup after a feed. This may fill him up and allow you to have a longer break.
Many mums want to know how long a breastfeed should last and there really is no correct answer! It does get quicker as the baby gets older - particularly once breastfeeding is established. Feed your baby when he wants and let him take as long as he needs. Sometimes baby will want a quick feed, other times he'll want to linger. Be led by your baby and you can't go wrong.