Is that 1 hour door to door or one hour train plus commute either side (this will make a huge difference).
In general id say 1hr door to door is really the upper limit, ultimately the longer the journey the more time you have to add in contingency (the more factors like weather/congestion/signalling issues also come into play), also remember the train schedule is unlikely to pair perfectly with your schedule.. you’ll have group projects, things will run late, you might get impromptu opportunities pop up.
Id also say anything more than 45 minutes will probably start to impact your scheduling, and if you plan on traveling ore then 30 minutes it will probably significantly impact your university social life, your ability to integrate into the university social community.
Ultimately it’s all about balance. Less then 30min will give you the best experience, the more over this the more you compromise, id recommend a 1 hour limit on max door to door single leg.