I love tape extensions. Seriously I don't know why you would buy them ready made. Its cheaper to buy a weft of your choice, then stick the tape on. The tape itself is designed for wigs and can be worn causing no damage to your hair. You can also then customise the size of the wefts to suit your client.
I had a beauty works celeb choice weft in for 10 weeks! It was way too long and needed reapplying after about 6 but I was road testing the tape lol. Even after 10 weeks the tape didn't want to budge. It can get a bit messy though but have a practice and its a very cheap, quick and effective method for short term use. I call mine express extensions.