There are no hard and fast rules; everyone’s different and you won’t appreciate your own limitations till you’ve been pumping for some time. However, it’s always best to err on the side of caution and slowly build up your sessions using low pressure. If you start to feel uncomfortable, stop. Make regular visual checks and take breaks. You can also spit your routine into two or three sessions throughout the day, to maintain the bloat. Research the various sites and get as much of a feel for things as you can, only you can really decide.