On the second day of CNY on 4th Feb 2011, I went to a temple to pray to Grand Duke in the afternoon. Later as I was outside the temple, a woman selling tassels and other curios was telling me and other people that those who offended Grand Duke of Jupiter should only start praying on the 4th day of the lunar calendar of thenew year and that if we pray early it is not correct and we need to pray to him again.
Secondly, if in the previous year we succumbed to Grand Duke or Tai Sui in a particular temple, we'll need to return to the same temple to pray and not change another temple or else we will be forever owing to Grand Duke. Is this true?

Yes, indeed, these are really two never-before-asked questions in this forum. However, the question should belong to the topic: Chinese Culture... than Fung Sway...
To fine-what the lady said; usually this is the recommended timing:-
Datewhen to Pray (converted to Western date)
6 Feb 2011 (4th day of Lunar New Year) best forDog sign to pray
8 Feb 2011 (6th day of Lunar New Year)best day for Rat sign to pray
13 Feb 2011 (11th day of Lunar New Year) best day for Snake sign pray
17 Feb 2011 (15th Lunar day) best day for Rooster to pray
Your second question: "Secondly, if in the previous year we succumbed to Grand Duke or Tai Sui in a particular temple, we'll need to return to the same temple to pray and not change another temple or else we will be forever owing to Grand Duke. Is this true?"

This is simply known as "playing-it-safe" to return to the same temple.
Further to what I mentioned, just imagine, if you purchased something only Harrods of London carries. And assuming there is only one store; sure enough if you need an exchange of sorts; you may have to (usually) return back to Harrods. Most stores practise such things unless; they have other avenues which you still often must call up to confirm.. first..

Quote

On 2/6/2011 8:02:33 AM, Anonymous wrote:
On the second day of CNY on
4th Feb 2011, I went to a
temple to pray to Grand Duke
in the afternoon.
Later as I was outside the
temple, a woman selling
tassels and other curios was
telling me and other people
that those who offended Grand
Duke of Jupiter should only
start praying on the 4th day
of the lunar calendar of
thenew year and that if
we pray early it is not
correct and we need to pray to
him again.Secondly, if in the
previous year we succumbed to
Grand Duke or Tai Sui in a
particular temple, we'll need
to return to the same temple
to pray and not change another
temple or else we will be
forever owing to Grand
Duke. Is this true?

Thanks. You saved me a third trip to the temple. As I am a Rooster, I will pray on or after the 15th Lunar New Year.