Accumulating a collection of plant or insect specimens can be useful to you and others. Remember to label each one with place and date of capture! They’re useless to anyone else without that. Read up on how to preserve them – archival paper, well-sealed boxes, etc. It may be useful from time to time to put the specimens in a plastic bag and put them in the freezer, to kill pests.
If your interests change and you no longer want your well labeled, well cared for specimens, donate them to a herbarium, museum, etc. (And once you do, let go of them emotionally. The institution may keep them for its own collection, exchange them to other institutions, or use them for teaching. If you care, discuss that before donating.) Put a clause in your will donating the specimens and associated notes to an institution. (You can specify which one or leave that to the executor of your will.)