Yeah one LFO can drive more than one chip. Using the Echo Base method you just need a separate PNP transistor for each chip, then you can either have one depth control hooked up to both transistors or hook 2 depth controls up to the LFO, so you could have different amounts of modulation on each chip.
You'd get some pretty mad sounds if the 2 PT2399s were in series though, because the modulated signal from the first chip would then get modulated again by the second chip, might sound great might just be a complete mess.
The reason
Taylor i have posted somewhere how to control the delay time of 2 chips only with one pot, instead of setting the 2nd chip with a fixed time. This may be worth adding
Yeah that's definitely worth looking at, the reason I did it with a fixed delay was that was the simplest way to do what Valoosj wanted, which was just more delay time.