Question: Will I get the same amount of prints/pages from a refilled cartridge?

Answer: As for volume, yes you will have the same amount of ink in a refilled ink cartridge as you would have in a brand new, store-bought cartridge... if not more.  At one time HP produced cartridges with the product numbering ending in "A" and the same product number ending in "G".  This threw many people for a loop.  Cartridges ending with "A", like 51626A, were manufactured with 40 ml, where the ones ending in "G", referred to as the economy version, where manufactured with 19 ml.  If you are refilling the economy version, good news, the cartridge that you bought with 19-20 ml in it can be refilled to 40-42 ml!  (This also goes for the HP 51645 series and many of the color cartridges too.) Exactly - HP just filled the cartridge half way up and sold it as such.  The "economy" cartridges have recently been discontinued.... wonder why?

   As for the amount of prints you receive from the cartridge, that will completely depend on what you are printing.  For example, say you printed mainly text or about 5% coverage per sheet with the cartridge when you originally bought it, then you refill it and print pictures at 25% coverage.  The cartridge is going to run out much faster printing pictures than it would just printing text.  This has absolutely nothing to do with the refill, it has to do with how much ink you are printing with.  You will probably find that the cartridges don't last as long because you feel you can print more since you have found an affordable way to do so!