Id pass on windows 10 this early in the game. LOTS of bugs as with any new release. Windows 10 will be a free upgrade for a year which gives them time to release some service packs.
Personally, 3-5 is a lot to expect out of a laptop(assuming, who buys desktops anymore?!) these days. Things are moving exponentially in terms of hardware requirements. If you were serious about the 3-5 thing id go with either a macbook or a thinkpad. Macbooks will hold their value better than just about anything out there. Thinkpads are durable as shit and will physically last 3-5 years of hard use. HPs business class of laptops are another good choice. personally, id avoid Asus/Dell like the plague.
As for specs, Absolutely no less than 8gb (16gb if you can afford it) memory, and a newer i5 (i7 if you can afford) processor. Dont buy anything with a mechanical drive. Solid state is the way to go. As mentioned, this all comes down to how much you want to spend.