There are a lot of variables, from your lifestyle to weather conditions to hair properties. The Devachan salons may well have a controlled environment, air conditioning maintaining a fixed temperature and humidity level. It probably helps having someone style you that can see 360 degrees of your head. Have you seen the before and after threads?

Post your before & After CG pics
Before/After for Wavies
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect