Related על זבחים 157:3

The [bitter] lettuce and the matzah and the Passover offering are obligated on the first night of the [Passover] Festival, and on the remaining nights [partaking of them] is optional. Rabbi Shimon says, it is an obligation for men but optional for women. Hillel the Elder would wrap all three of them together and eat them. From what time are they eaten? They are eaten once it gets dark. [If] he did not eat them once it got dark, he may eat them [at any time during] the whole night. [If] he did not eat them [at any time during] the whole night, he cannot eat them from then on. The [bitter] lettuce and the matzah and the Passover offering -- one does not prevent fulfillment [of the obligation] of the other (e.g., if one lacks the bitter herb, he can still fulfill the mitzvot of matzah and the Passover offering).