Yes, 5 hour limit is same for Power Bi Premium per user and Premium per capacity both and that can not be increased as for I know, you mat reach to Support https://powerbi.microsoft.com/en-us/support/pro/
Suggetion - To have sucessfull refresh you will need to reduce data volume or pick a non peak hour to do first full refresh and then go for incremental refresh
You can also look for Gateway or source performance as that could also be bottleneck
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