I would also suggest that maybe your planning is a little too involved - scrutinising the NOTAMs etc. for absolutely every airport on your route might not be necessary (though I'm not sure where you're flying) - will the weather vary massively for each airfield? In emergency or abnormal situations ATC can be used as a resource to gain frequencies, check weather, pre-warn airfields etc. I'm not saying be slap-dash and don't plan but I would say an overview of the weather on the route - obviously focussing on departure, destination and nominated alternate - is suffice. The NOTAMS for the above airfields are obviously important too but not every notice for every airport along the route.
I agree with those that suggest the time is adequate - maybe you need to adjust your planning to fit around a more realistic timeframe, one that you probably will have to work around for tests and in the real world of flying, where flexibility and changes are the norm?
One of the key skills of flying professionally is picking out the pertinent info and prioritising tasks - there will always be too much paperwork to look at and you'll need to get used to actively looking for the important stuff.
I fly commercially - if myself and the captain read every word of the briefing pack we'd never leave on time (and on-time performance is part of being a commercial pilot!) - maybe you could practice by giving yourself routes and then planning them in restricted timescales. Practice makes perfect! I completely understand the desire to be well- (even, over-) prepared because I was the same and planned to the nth degree but over time you will learn what is important to commit to memory, what to write down and what you can gain from other sources (e.g. ATC, the charts, etc.) in a reasonable timeframe if you need it.
Just some thoughts...
Good luck!