The navigation element of the LST requires discretion from the FE, who should take the pilot's recent experience into account.
Paradoxically, someone who hasn't flown for 4-ish years is more likely to have received recent refresher training than someone who is a few months out of date and who had done nothing more than a few £100 cup of coffee trips in the previous couple of years.
But if your test includes more than the LST specifices, you lay yourself open to Regulation 6 action.
I was asked about an LST for this sort of thing by a fellow FE recently. He had been quite satisfied with a 20 min navigation sector from the applicant - because the applicant had flown several dual navigation trips in the previous fortnight's refresher training.
I certainly wouldn't expect to fly the entire PPL Skill Test for a SEP Class Rating renewal.