First of all, since Adam, there has been a record of how long people lived and how old they were when they had children (ex. Genesis 11:14, 32). So the lineage up to date is approximately 6,000 years old. The only place that I know that Gap Theorist (old age theory) try to put millions of years, is in the creation of Genesis.
It also doesn't fit in creation.
Of what I know, when million of years are inserted into the Bible they are inserted into the 7 days of creation. This creates a major problem with the day light cycles. God called the light Day, and the darkness He called Night. So the evening and the morning were the first day (Gen 1:5). The literal meaning is: And evening was, and morning was, a day, one. If the first or if any of the other 7 days of creation were millions of years there would be thousands or million years of morning (day) then thousands or million years of evening (night). The Bible says evening and morning, not evenings and mornings. If there were thousands of years in creation, evening and morning would be plural not singular. This day light cycle would create a very different climate on opposite sides of the earth. The side that was exposed to morning would be insanely hot and the side with the evening would be insanely cold. I dont know of any animals that could withstand the kind of climates that would be created from this effect.
Also God created birds before reptiles. Birds and sea creatures were made on the fifth day (Genesis 1:20-23) and on the sixth day land animals and man were made (Genesis 1:24-31). Also there wasnt death before man ate the fruit of knowledge of good and evil (or before he sinned). Therefore, just as though one man sin entered the world, and death through sin , and thus death spread to all men, because all sinned- (Romans 5:12). This means that nothing died before Adam sinned. So over the millions of years that Gap Theorist believe in, there would have been no death and no fossils. Constantly the Bible says that he created his creation, not that it evolved (Genesis 1:24, 25, 27). These are just a few things that refute the idea that evolution and the Bible are compatible.