I have done this re-greasing malarky twice, the first time with a high quality grease recommended for the job on a set of rear struts on a 55 plate blobeye. Lasted a week and had to change the struts replaced them with KYB's. These lasted 2 years, thought ah well might as well try it again, but this time used heavy duty aircraft strut grease lasted 15 days and then repalced all 4 struts with KYB Ultra's havnt had a problem since - touch wood. It is worth checking there is no play in the top mounts but in my opinion you are wasting your time repacking them.