As follow up - I contacted AerClub directly and got this response:

"Avios redemption seats booked through www.avios.com are available to purchase on routes with Aer Lingus outside of 60 days. "

So it looks like you were spot on with the 60 Days!

Is this a new "benefit" or have i just not noticed this before? Wonder if they are trying to encourage the burning of Avios through the Pay With scheme on main site.