Yes, like some people here I think that drugs effect should last longer, maybe forever,
but the drawbacks should become worse and worse over time. Taking another dose of your drug would set drawbacks back to normal status.
For example...
Jet effects as they are right now :
Immediate: +3 to Maximum Action Points, +1 to Strength, +1 to Perception.
After 3 hours: -4 to Maximum Action Points, -2 to Strength, -2 to Perception .
After 6 hours: +1 to Maximum Action Points, +1 to Strength, +1 to Perception.
Of course, this is in-game time. I am too lazy to calculate, but the worse drawback (after 6 hours) is like after 15 minutes in real life. So "good" drug effect lasts like 5-10 minutes, drugged characters know this better than me.
With my idea of a longer good effect, and increased drawbacks over time, it could be like this (with a removal to SPECIAL bonuses for good side effects, as it would last longer).
Immediate: +3 to Maximum Action Points, -1 to Perception, -20 kgs to Maximum Carry weight.
After 20 hours: -4 to Maximum Action Points, -1 to Strength.
After 40 hours: -1 to Maximum Action Points, -2 to Perception.
After 70 hours: -2 to Strenght, -2 to Perception, -2 to Charisma.
After 120 hours: -1 to Maximum Action Points, -2 to Perception.
This way after 120 hours (that's very approximately about 5 hours real time) without taking a single dose, you would have severe drawbacks and would become a poor, almost helpless junkie.
Taking one dose at any time would remove all the effects and set instead the "Immediate" one. Of course it is only an example here. Together with these changes, jet doses should be rarer, drugs combinations could maybe be removed, etc. Also, the "After X hours" are just random values, like the drawbacks here. I just think the future of the drugs is in a long effect of them.