Approximately how long does each stage of lung cancer last, to the best of your knowledge?

There's no answer: Little precancers can sit and smolder for years, or seem to arise from previously-healthy areas overnight. We essentially never see "stage 1 oat-cell carcinoma of the lung", so this stage of this cancer must not last very long. And some slow-growing cancers allow people to survive for years with known stage 4. Lung cancre itself is a few dozen different diseases, each with its own quirks.

Stage I longest: Cancers grow by Doubling times (dt) as each cell divides (1cell-2-4-8 etc) So it takes the same time to go from 1 to 2 cells as it does to go from 3cm (Stage I) to 6cm (Stage 4). The average dt for lung cancer is about 120 days. It takes 20 dt to go from 1 cell to 1mm (smallest we can see on CT) =approx 7yrs. For next 4 years it is still less than 2cm (Stage 1) but 2 years later is Stage 4.