On age in shidduchim, the Rebbe's guidance:
A large age gap between partners is not required, according to Chazal (IK 2042), and age differences are not always significant in themselves. What matters is whether a feeling of closeness grows over time; if it does, it will likely keep improving (IK 6889).
Where there is a large age difference, or the other side is older than usual, look into it carefully, including why the match was delayed, before deciding (IK 8038, 8234). Examine one's own motives honestly; if outside considerations are not driving the decision, one can proceed with confidence (IK 10494).
For young women, there is no need to rush. In one letter the Rebbe advised patience, putting a young woman's growth and education first before thinking about engagement (IK 7197).