I can't find anything there about 3 months expiry (happy if someone finds it as I had a brief look but could be missing it)
Terms and conditions
http://www.velocityrewards.com.au/content/ProgramBenefits/TermsConditions/index.htm#10
Complimentary Lounge Pass
9.14 We may provide you with complimentary Virgin Australia lounge entry from time to time (Complimentary Lounge Pass).
9.15 Provision of Complimentary Lounge Passes will be in our sole discretion.
9.16 The Complimentary Lounge Pass will expire three months after the date of issue.
9.17 For access to a Virgin Australia Lounge, present your Velocity Frequent Flyer Membership Card together with your flight itinerary or boarding pass for onward domestic travel with Virgin Australia.
9.18 Complimentary Lounge Passes are non-transferable and must be used either:
9.18.1 by the Member; or
9.18.2 where the Member is otherwise entitled to access the Virgin Australia Lounge, by a guest accompanying the Member into the Virgin Australia Lounge.
9.19 Access to the Virgin Australia Lounge is only permitted for the day of your travel on Virgin Australia and is at the discretion of the Virgin Australia Lounge staff and is subject to any capacity restraints that may be imposed.9.18.2 where the Member is otherwise entitled to access the Virgin Australia Lounge, by a guest accompanying the Member into the Virgin Australia Lounge.