how long does chilling take for this icecream recipe

IMHO, there is no single answer to this question. It largely depends on the way you are "chilling". It ranges from:

• Leave the pot on the counter until cooled to room temp, then stick it into the fridge until cold. Could be anywhere in the range of 2-6 hours, I guess.

with a bunch of variations up to:

• Transfer custard from hot pot into a flat, pre-chilled metal bowl or baking tray, plunge bottom into a salted ice bath (or pile of snow if it's freezing outside) and stir constantly with a rubber spatula. Should be cold within minutes.

So what would I do? I'd make the custard a day in advance, let it cool somewhat, then freeze the cubes over night. Never bother about the given 4 hours first freeze, because I assume this is a minimum time to get the cubes frozen fully. Finish the ice cream 4-5 hours before planned serving time the next day, because it might get too hard if frozen too long, but this depends on the recipe and I can't say for sure what the texture would be in this case.

It is not only about getting the temperature of the base down, but also about some molecular processes going on in the base after pasteurization that take some time. This is why it is generally recommended to let an ice cream base ripen some time before churning it.

It is common to age mix for anywhere from 4 to 24 h. Crystallization of the fat in the emulsified state occurs more slowly than when it is in the bulk state (not emulsified). Fat crystallization rate depends on the type of fat and emulsifier used (Adleman and Hartel 2001 ), but generally requires up to 4 h for complete crystallization (Barfod et al. 1991 ). [...] Further, there is considerable rearrangement of molecules at the fat globule interface. The adsorption of proteins that occurs during homogenization does not lead to the most energetically favorable interface, particularly in the presence of low molecular weight emulsifiers. At aging temperatures, the emulsifiers displace protein at the fat globule interface (Gelin et al. 1994 ).

[...]

Freezing of improperly aged (“green”) mixes leads to ice cream characteristics similar to those found with nonemulsified mixes. Namely, there is less retention of shape and relatively fast meltdown due to less than optimal destabilization of fat during freezing.

Goff, H. & Hartel, R. (2013). Ice cream: Seventh edition. (p.139) 10.1007/978-1-4614-6096-1.

I also have big doubts that the food processor method described in the linked recipe will lead you to good results. One of the most important keys to a well textured ice cream is to avoid the creation of ice crystals larger than 40 µm. Freezing the base to solid blocks and then stick it into a food processor won't get you even close to this scale. Even the most simpelst and cheapest ice cream makes using a pre-frozen bowl should yield better results.