In my case,i went to india in dec 2008,came back in april 2009,applied for citizenship in may 2009.You have to be at the same address for more than 3 months before you leave the country & should come back to same address.
Its my opinion.
I-130 for parents
09 June,2012-Applied I-130 for Parents
15 June,2012- Check's Cashed
19 June,2012- Case number received
08 September,2012- Received approval notice
RFE ,docs sent on 31st dec 2012
01 Feb 2013-Interview letter received
I-751 for wife
25 September - I-751 - Sent
27 September - I-751 - Delivered
02 October - Check cashed
04 October - Extension notice received
13 October - Received bio-metric notification (Fingerprint notice - Scheduled for 07th Nov)