One of the interesting things in the Bible is that there oftentimes is no indication of the passage of time, be it hours, days, weeks, even longer.
Look at the book of Acts, for example. It is a good documentary of what happened starting with Christs' ascension. When reading it, one may think it all happened over the period of a couple weeks, perhaps. But one has to look for clues to determine that a gap of years may have elapsed from one verse to the next. Consider Acts 14 & 15. Paul and Barnabas went to Iconium, Lystra, Derbe, Pisidia, Pamphylia, Perga, Attalia, and then sailed to Antioch. Whether walking or sailing, going from city to city was not done at 60-70 mph as we can drive today. So it was a fair number of days between each town, where they stayed some indeterminate length of time at each. But after being stoned in Lystra, given the lack of medicines that are common today, one can figure that Paul spent a month or so somewhere recovering from the stoning before moving on. Look at Acts 14:28 And there they abode long time with the disciples. How long was that?
So, I think it's reasonable to conclude that some passage of time happened between Matthew 27:51 and 52-53. This is confirmed in 1 Corinthians 15:20-24.
Matthew 27:51-53 (KJV)
51 And, behold, the veil of the temple was rent in twain from the top to the bottom; and the earth did quake, and the rocks rent;
52 And the graves were opened; and many bodies of the saints which slept arose,
53 And came out of the graves after his resurrection, and went into the holy city, and appeared unto many.
1 Corinthians 15:20-24 (KJV)
20 But now is Christ risen from the dead, and become the firstfruits of them that slept.
21 For since by man came death, by man came also the resurrection of the dead.
22 For as in Adam all die, even so in Christ shall all be made alive.
23 But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming.
So, what happened to them that arose out of the graves (their souls had been in Paradise and Jesus led captivity (Paradise) captive (Psalm 68:18 and Ephesians 4:8) to Heaven with Him. But their physical bodies? I honestly don't know. We do know that our physical bodies cannot survive without oxygen, so they got new spiritual bodies on the way to Heaven. The Bible doesn't say what happened to them after they were arisen. Neither does it say what happened to Lazarus after Jesus raised him from the dead. Did he live another 2-3 years? 10 years?
I guess it all comes down to this: do we care? We can ask Abraham, Moses, David and the rest how'd they get from Paradise to Heaven and what happened in the intervening time when we see them. For those of us that will be raptured any day now, we will be transformed in the twinkling of an eye. Were the OT saints and deceased believers of Jesus (that Saul and other jealot Jews like him likely had killed) similarly transformed?
1 Corinthians 15:52-53 (KJV)
52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
53 For this corruptible must put on incorruption, and this mortal must put on immortality.
