Will I be qualified to apply for ILR??

Hello.
I've just got extension approval in January for my Tier 1 visa, but I have been wondering whether I'd be qualified to apply for Indefinite Leave to Remain once this one is to expire.
I've received a HSMP approval letter back in June 2007 and have requested for the actual visa in Dec 2007. But I didn't move to UK until July 2008.
so at the time of next visa renewal, I'd be staying in UK for less than 5 years.
Will I be able to apply for Indefinite Leave to Remain after my current 3 year visa or need to apply for another Tier 1 extension??

(I've worked under work permit prior to HSMP, but I was back home for 1.5 year so I believe I can't count this period into consideration...)
Please share your knowledge.
Thank you so much in advance!

Under current laws, a second extension is needed if leave to remain expires more than 28 days before the 5th anniversary.

regards