"Fill in the intervals" sounds to me like "accumulate". I interpret "accumulate" as something that happens in the body, but "condense" as something that happens to the pleasure.
Right now I'm thinking that the blunt force meaning is of the PD something like "if you make all of the external, objective aspects of various pleasures equal, then the pleasures will be equal". So this seems to say that pleasure itself, the pathe, is a specific thing (maybe an on/off switch), and the only differences between pleasures are where in the body or mind they occur and for how long. "Condense" would imply an additional difference in intensity, "accumulate" would not.