Objective: A “PROficiency based StePwise Endovascular Curricular Training” (PROSPECT) has proven its superiority over traditional training in a randomised controlled trial to acquire basic endovascular skills outside theatre, but real life adherence is low. This study aimed to compare the original distributed training format, where trainees learn at their own pace, with a massed training format offering the same content within a limited time span while exempt from clinical duties. Secondly, long term skills retention was evaluated. Methods: A multicentre, prospective study allocated participants to the distributed D-PROSPECT or to a massed, compact version (C-PROSPECT) based on logistics such as travel time, participant and instructor availability. A multiple choice question (MCQ) test (max. score 20) tested cognitive skills. Technical skills were assessed using a global rating scale (GRS) (max. score 55), examiner's checklist (max. score 85), and validated simulator metrics. Data were collected pre- and post-programme and at three, six, and 12 months after programme completion. Results: Over four years and in two countries, D-PROSPECT was implemented in two centres and C-PROSPECT in three. A total of 22 participants completed D-PROSPECT with a 41% dropout rate, and 21 completed C-PROSPECT with 0% dropout rate. All participants showed significant improvement for all performance parameters after programme completion: MCQ test (median 14.5 vs. 18; p < .001), GRS (median 20 vs. 41; p < .001), examiner's checklist (median 49 vs. 78.5; p < .001), and simulation metrics (p < .001). Scores of C- or D-PROSPECT participants were not significantly different. No significant differences were seen between groups during the retention period. Conclusion: PROSPECT significantly improves the quality of simulated endovascular performances using a massed or distributed training format. A massed training format of PROSPECT may be preferred to decrease dropout during standardised training to obtain basic endovascular skills in existing surgical curricula.