With the new dilithium exchange going live, I did some maths and made an interesting discovery today that probably means I'll stay at my current subscription level when the game goes f2p.
Thanks to picking an annual sub when the game launched, I'm only paying £6.14 a month and the monthly stipend will be worth £3.20. This means I will effectively pay £2.94 for gold membership.
£2.94 in c-points is 367.5 (call it 368), which is worth between 18,400 and 184,000 dilithium (or between 2.3 days and 23 days refining limit) based on the exchange limits. This means that it shouldn't be too hard to actually make back my remaining sub in c-points.
This compares to a lifetime subscription which costs £192.49 and would take just over 2 years and 7 months to pay off at the same rate as my current sub or just over 5 years if just the monthly 400 c-point stipend is taken into account.