Is it possible that a skin product loses its efficacy after repetitive use or is it me?

Some products worked wonders on my skin but after months of usage twice a day I didn't notice anymore noticeable improvement/effect on my skin and I'm back to square one. Is it me or the products?

I have tried some soaps, scrubs and creams to help fight persistent acne scars on my face and other parts of my body. Here are some of these products:
- Rosance scrubing soap
- Aveeno brightening scrub (after buying 3 times, I suddenly became allergic)
- Rosance X-20 (aqua, glycyrrhiza glabra, aspergilus ferment, ethoxydiglycol, propylene glycol, reseda luteola, arctostaphylos,  uva ursi, carum petroselinum, dimethicone copolyol, triethanolamine, 4-benzophenone, PPG-26 Buteth-26, PEG-40, hydrogenated castor oil, parfum, Xanthan Gum, EDTA, Sodium Metabisulfite, Benzyl Alcohol, Methylchloroisothiazoline, Methylisothiazolinone, hydroxycitronellal)
- St-Yves scrub

I can also name some products that never worked for me since day one (Neutrogena non-oily cream, Neostrata...) but have proven to be a frustrating lost of money, time and energy.

One more question: are there any products on this earth offering permanent results? I'm afraid all the products on this planet are confected so that you have to buy them for the rest of your life.