Im sorry to break it down to you ladies like this but glue in extensions are very damaging to your own hair. My friend is a hair specialist for extensions and if you knew what mess she has to repare after the glue ins you would never ever wanna get them done! They are good if you want them for a few months, but definitely not when you want to have them for years.
At this moment, the best optionhere in Europe are so called Bond Plus 2 extensions (or eurolocs). Especially if you wanna have extensions for years. To explain the system: your own hair and extension hair is put into a small plastic piece (bond) and the is heated so that it holds well together. The human hair extension has a small metal piece which holds with the plastic piece (after being heated by a special gadget). This method is very similar to the micro rings method which is a strand by strand method but doesnt cause any damage.
I have this method myself and I can only recommend it. However, I dont know if this method is done in the US... Over here all celebs have it because you can keep reusing the hair for years - there is no glue (or keratin adhesive as they now call it). It is very easy to take out and this method is also very easy and fast to apply.
I have got added 40 strand in 18 inch just to make my hair a bit thicker and it took only 1 hour. You can color, perm, straighten, curl the hair... Just like your own hair. My friend got added for example only 20 strands as highlights because she has fine hair and processing would damage it.
You have to go about every 2 months to the salon to get them moved back closer to your scalp (they should be about half inch from your scalp, not directly close to it).
Im not an expert, just sharing some experience