How much experience does a writer need?
Lyric poets in partcular seem to be able to write just fine without having exprienced anything beyond childhood and adolescence - because, in terms of subjective time and strength of emotions and perceptions, childhood is the main time of life.
Hence, poets can produce first rate work at a young age, and many excellent poets never get much beyond the subject matters of chidlhood and adolescence (e.g. Dylan Thomas).
Adolescence is useful because the experience of being in love opens up a lot of possibilities; experience of marriage and having a family completes the requisites and perhaps exceeds them even for a novelist with a broad social canvas; since writers as great as Jane Austen have not themselves been married or had children (although they have experienced these vicariously, via family).
Adult experience is - by contrast - generally a shallow and inessential thing to a writer; in fact it is more often a snare than a help - probaby because it is neither so intense nor so fully assimilated as early experience.
Writers that write mostly about their adult experiences are generally below even the second rank, and among the best writers adult subject matter usually corresponds to their lesser works.
For instance, when Saul Bellow writes about his childhood and teen years, he is a great and magnanimous writer; but when he write about adult things he is pretentious, spiteful and petty.
Another example: Robert Frost's later satirical and topical poems (from his experiences as a famous man) are at a generally lower level than his earlier work; although Frost's greatness - his much greater strength-with-range than most other lyrial poets - came from his having retained an extended child-like sensitivity to experience (an innocence) until he was about forty, when he began publishing poems.
The common practice of gathering experience in order to write about it (like the genre of 'travel writing') is fundamentally a fake activity; and that comes through into the writing as the flaw of dishonesty, which works like a crack in a china vase - the writing does not ring when tapped, but merely emits a dull crunch.