Pairing — occasionally include nipple touch when already highly aroused (near orgasm, solo or together), and see over weeks whether an association builds. Research-wise this is a direction, not a technique: human sexual arousal can be conditioned, and one study even ran a two-week at-home paradigm with orgasm as the reinforcer — but every study conditioned pictures or scents, never touch. The transfer to real nipple touch is untested.
Carry three limits with it. One: subjective liking doesn't automatically follow conditioned physical response — 'the association never turned into liking' is a normal outcome, not a failed trial. Two: conditioned associations fade and depend on context — what built here may not show up there. Three, and most important: if nipple touch already reads as aversive, painful, or uncomfortable, repeatedly pairing it at high arousal can consolidate the aversion, not dissolve it. If things move in the bad direction, stop; this door is closed.
Timing — some people report that sensation differs by time of month. Keep that at anecdote level. What is documented: breast tenderness and swelling fluctuate across the cycle, peaking in the late luteal phase — a pain measure, not an erotic-sensitivity peak, so read 'most tender' as 'lighter or skip', never as 'best moment'. Reported changes in desire and lubrication are highly individual with no uniform pattern — and cycle tracking doesn't apply on hormonal contraception, during lactation amenorrhea, or perimenopause.
Both directions are 'notice occasionally' material: no schedules, no tracking duty. Either can stay closed.