The effects of an ECA stack will continue beyond the subsiding of the stimulant effects, so you don't really need to up the dosage way too high constantly in order to feel the stimulant sides. Here is a long term study with the EC stack.
The acute and chronic effects of ephedrine/caffein... [Int J Obes Relat Metab Disord. 1993] - PubMed result
This paper describes a 24-week open follow-up trial with reduced obese patients all receiving an ephedrine/caffeine combination (20 mg/200 mg) three times a day. The study was a continuation of a previous 24-week double-blind placebo-controlled study where the ephedrine/caffeine mixture had shown superior weight-reducing properties when compared with either ephedrine alone (20 mg) or caffeine alone (200 mg) three times a day. The medication was stopped between weeks 24-26 in order to evaluate withdrawal symptoms. The follow-up period was from weeks 26 to 50. Of 127 patients included, 99 completed the follow-up treatment, which resulted in an additional weight loss of 1.1 kg (P = 0.02). Adverse drug reactions were all minor and temporary.
We conclude that the ephedrine/caffeine combination is safe and effective in long-term treatment in improving and maintaining weight loss. The side-effects are minor and transient and no clinically relevant withdrawal symptoms have been observed.
The reason why this study ran so long is because contrary to popular belief, unlike Clen, EC stacks don't need to be cycled in the same way. They illicit a response from all beta receptors, more specifically the beta 3 which don't have the same downregulation that the beta 2 receptors undergo when using something like clen.