It depends on the woman. I started doing just girth exercises a couple years ago. When I broke 6 inches my wife admitted it made her apprehensive and so she couldn’t relax. But at the time the gains came extremely fast as I went from 5.5 to over six in 3 weeks. Don’t know why, other than my winky seems to like girth exercises.. So I quit exercises for a while and let it go down a little. Then she felt better.
In the last few months we’ve also had to take it easier because she’s past menopause and the playground is not as wet as it used to be. She admitted she could probably take a little more length but she’s leery of increased girth. However, coconut oil and being patient and slow to start may allow a little more width.
Keep in mind, length and girth are determined by the woman’s parts, whether she’s had kids naturally, age, and her past sexual experiences. How tall she is can also come into play. A 5’10” woman will typically (but not always) be able to handle more than a 5’ 1” woman