A second conversation is reasonable when there is a genuine update or new reason to reconnect.

Networking works better as a relationship than a one-time transaction. Six months is enough time for your situation or their perspective to change.

You could mention that you are now preparing to apply and would value their perspective on one or two specific questions that came up since you last spoke.

Reference the prior conversation, give a brief update, and make the new ask specific. If useful, this guide on consulting coffee chats gives more detail.