Do you think travel sizes are worth buying?

Trying to be more conscious about my makeup spending, I've come to realize I actually use a lot of travel or deluxe size makeup products, especially mascara. I have a travel size Laura Gellar Gilded Honey highlighter that I've used every day since last Fall and it's still going strong. It'll be months before I would ever finish it. It makes me think about buying certain things in full size and if I'll really need that size or if I'll have the will power to finish it all before moving onto other products. I can see how buying a full size foundation or concealer (something you use daily) would be beneficial. I guess value wise a full size is more bang for your buck, but is it truly if you don't end up using it all?

Does anyone else like using travel sizes? Do you think it's a good strategy to spending less?