Things are different for people working in the shop and DIY guys without easy access to a truck.
I am slowly building a nice collection of tools (I started with Home Depot and Auto Zone tools and from the beginning of this year I decided to learn more about tools and am slowly building my collection of Snap On, SK, Craftsman from Springfield (-V- and =V=) and other old American tools.
Warranty: when I was growing up we did not have lifetime warranty. It is a great plus, but not a must. However, to me it shows how that company treats it's customers. Based on that I consider how much I am ready to pay for the tool and how much I will recommend the company to people around me.
Some examples of my real life situations:
SK - I have some tools by SK and buy them when good opportunity comes. Some time ago one of the old sockets developed a small hairline crack. I got in touch with SK and asked about warranty. They asked me to send a piece for examination and replacement.
Even though I never sent it (the socket was pretty old...),the offer showed good will of the company to resolve the situation. I keep buying their tools and recommended them to multiple people.
Tekton -Definitely goes out of it's way to help you. I had a problem with MIT torque wrench which broke. I got a great treatment and not a kit, but the whole wrench. Even though a lot of professional guys say different things about the company (professional vs DIY grade), great customer service trumps 10% difference for majority of DIY guys. I will keep using their tools and recommended them to a lot of people (which created a lot of customers over a long time and will spread the word further and further). Unless people really want SO, MAC or SK name, the quality is great for what majority of non-professional people will ever use those tools for. Small steps will make this company greater than Craftsman in its' best days. Their increase manufacturing in US makes it much more likely for me to recommend them and hope the best for their company!
Snap On - called about the socket which developed a small crack (old socket, but in good shape, not sure how it was used before me). I am not going to lie that I or my dad bought something new if we did not. Fair enough, no warranty, no big deal. However, I now buy Snap On only at cheap prices (though if I really need something, I have no problem buying it new - like a new handle for old SO carry box which I hope to restore). The only thing which gets affected is how much I am ready to pay for used SO tools when I need some extra tools. Overall, lack of real lifetime warranty for everybody does not affect the company, but affects how much DIY guys will pay for a used tool to a person selling old collection...
My best suggestion - use the tools which feel the best in your hand, make you smile when you use them. If there is no warranty, just buy the tools cheap enough that if it breaks, you do not feel bad and buy yourself a replacement. Overall, majority of our tools survive years and years and very few ever broke in my hands...
However, if you buy tool set as a gift to somebody, consider buying from a company with real lifetime warranty - gives an extra good feeling to a new owner even though he/she will hopefully never need to use it...