Halving magic item creation time

[WelshmanJones]

Core Rule Book wrote:

This process can be accelerated to 4 hours of work per 1,000 gp in the item's base price (or fraction thereof) by increasing the DC to create the item by +5.

1) Does this mean I can work at a pace of 2,000 gp of the item's base price in 8 hours, effectively halving the amount of days required to make an item? E.g, an item worth 4,000gp being made in two days as opposed to four?

2) Do I need to increase the DC by +5 for every 4-hour-block of accelerated work I complete? Or is it increased once, regardless of how many times I work at an accelerated pace?

[Fuzzy-Wuzzy]

1) Yes.
2) Just once, making it effectively all or nothing.

[Diego Rossi]

You make the check only once, at the end of the process.

You produce the item at a speed of 1.000 gp every 4 hours of work, but you are still limited to working on one item in a day and you still use 4 hours even if the item cost less than 1.000 gp, so you don't exactly double your speed.

[zza ni]

you can go up to 4k a day with a helper that has Cooperative Crafting feat (a valet familier comes with it build in ;)

[Wheldrake]

Magic item crafting is a wonky system anyway. Just work out the details with your DM. The DCs for crafting are so low that any reasonably optimised wizard doesn't have to worry about a few +5s here and there.