First: what you have is probably not a purge — a purge is breakouts (the retinoid accelerating pimples that were already brewing). Flaking, pinkness, and sting are retinization: your skin adjusting to retinoid-driven turnover. Both are common early, and both usually settle. On prescription-retinoid labels, irritation peaks in the first couple of weeks before easing (https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=08ab7e0c-1437-455f-815c-98904d96a289), and OTC retinol follows the same arc more gently.
"Push through" is half-right. The dose that matters is the one you can sustain, so make it comfortable rather than heroic: drop to two nights a week until the flaking calms, use a pea-sized amount for the whole face on fully dry skin, and buffer with moisturizer — before or after both work, and an "open sandwich" doesn't measurably blunt the retinoid's activity (https://www.jaad.org/article/S0190-9622(25)02062-6/abstract). More irritation is not more results; it's just more irritation.
The line where you actually stop: raw, cracked, weeping skin, rash-like itching, or stinging that's getting worse rather than better week over week. That's a barrier that needs a break — pause the retinol, go bland for a week or two, then restart lower and slower. Daily sunscreen is non-negotiable throughout.
On payoff timing, so you can calibrate hope: measurable photoaging changes take roughly 3–6 months of consistent use (https://pubmed.ncbi.nlm.nih.gov/2024983/). Week three is the hazing period, not the verdict.