Here's my rant about carry-on sized travel backpacks.... It's only a personal opinion.... Take it or leave it... But some of it may be applicable to your situation and travel style.
First of all, whether you're travelling for 2 weeks, 2 months or 2 years your backpack size doesn't change - you're bringing exactly the same stuff for a short trip or a long trip.
In my opinion for a normal hostel/guesthouse/hotel/etc. trip anything over carry-on size for commercial aircraft (about 40ish litres) is too big. Think light, efficient and mobile... you definitely don't need to be hauling around a boat anchor on your trip.
I travel independently for indefinite periods (several months at a time) via hostels/hotels through 3 climates with a carry-on size backpack with LOTS of room left over - all the cinch straps are yanked to their tightest dimensions so the backpack is really only about 35 litres.
That's including a set of nice clothes to crash an Embassy party or high-end club, normal day-to-day casual and hiking wear, beach clothes, personal hygiene products and everything else you need to be safe/comfortable plus a laptop, digital still/video package and all the peripherals.
It's easily doable and you'll see lots of experienced backpackers doing the same - and in warm climates going even lighter. Seeing other travellers - especially smaller women - struggle with 60-70-80 litre backpacks (usually with additional daypacks!) is insane for my style.
On another note I dislike zip-on attached daypacks like the Osprey Farpoint 55 for three reasons.
1.) They put weight in exactly the worse place possible, out and away from your spine.
2.) The attached daypack is useless for carrying anything valuable because it's out-of-sight and out of your control.
3.) I don't want a generic daypack forced on me, I want to choose my own daypack (or camera bag, or cross body bag, or murse, etc.) that fits my personal requirements exactly.
Speaking of daypacks... I'm not into looking like a stereotypical Lonely Planet backpacker so I don't carry the usual daypack during the day/evening. I want something that's small, unobtrusive and not out of place in a nice restaurant, bar or just hanging around. It's fine (in most situations) for carrying all I need for urban/semi-urban exploring, and it handles all my important essentials during flight travel, etc.
Going light makes sense for my particular style because it allows me to keep my backpack with me (almost) all the time - it's carry-on size for aircraft, it doesn't need to be checked into the baggage space under the bus where it's out of my sight and control - and it's obviously way easier/faster to navigate a crowded train aisle, keep with me inside the taxi, stow in a small boat, fit into a tuk-tuk, onto the back of a motorcycle and a million other situations.
The market for carry-on sized backpacks that are specifically designed for travel (as opposed to hiking/trekking) has absolutely exploded in the last decade or so. There are lots of really great options on the market. Here's a few examples (there are many more) in no particular order...
- Tortuga
- Peak Design
- Patagonia Blackhole MLC
- Osprey Porter 46
- Farpoint 40 for guys and Fairview 40 for ladies.
- Eagle Creek Tour Travel
- Base Camp Voyager
- Minaal Carry-On 3.0
- GORUCK GR2
- Nomatic Travel Bag
- Aer Travel Pack 3
- Cotopaxi Allpa
- Mother Load
- Tom Bihn Aeronaut
- Monarc Convertible
- Deuter Aviant
Everyone's needs/requirements are different though... different strokes for different folks... your style might be completely opposite of mine.
Lastly, have a look at r/onebag. Lots of super organized, minimalist travellers there too.
Good luck with your shopping/research.
Happy travels.
I'm currently in SEA for about 3-6 months, as with a lot of noobies doing a trip like this we got the Farpoint 40L aiming to onebag it as best we could.
My issue with it is even with the ability to pack light (warm weather... mostly), one third of the total weight you're allowed onto planes is the bag alone.
Don't get me wrong, the bag is great, but I just question why it's so heavily recommended. I'll continue to use the bag as long as the straps hold, but I'd be very hesitant to recommend it to anyone.