Posh,
It only takes me 10-15 minutes, but took me longer in the beginning! Do you have Windows/PC? If so, just search for what you are looking for (fall flower items, for example), and right-click and open in a new tab. Do this until you have a bunch of tabs. That way, you don't have to go back and forth so much. You can just close each tab as you copy and paste the URL. Maybe this sounds complicated, but I always have so much going on at one time that I'm used to it!
Another shortcut is to add things throughout the day to your favorites. When you're ready, add items from your favorites to your treasury. This way, all the items in your treasury are already items you love!
After I figured out these shortcuts, I started to go crazy and sometimes will make 2-3 treasuries in one hour. That way I can cross "make a few treasuries" off of my Etsy to-do list. My one treasury that made it to the front page was made in under 15 minutes. I had forgotten about it until I started wondering why I was suddenly getting so many hearts for it! Just remember to add all different shops, don't add your own item and add different types of items (not all jewelry, not all clothes, etc.).
Honestly, people look at treasuries for just a few seconds and then forget about them. It shouldn't take you that long. Don't "try to get on the front page" because front page treasuries get picked by hand, they don't get picked for being popular (they get popular for being picked).
Aman