i have this problem where i always make my sims relationships 100/100 by using the sim blender, as i cant stand all those notifications that happens at 4pm everyday. Can anyone suggest something else to break this habit and/or something that makes relationship decay slower or something?

They already decay pretty slowly. Do a group activity with group talk to boost STR to near 100. It will take while to go down to the notification level. The LTR will catch up. When you see the relationship has decreased to around 70, do a few interactions to recharge it. You have access to all strong actions once the LTR has risen, hug, appreciate, ask for every subject. Don't make friends for wants and only go to 50 level. They want to be friends with everything but the kitchen sink.

Pretty sure those notifications are moddable. At least I'm not much bothered with them anymore; don't remember the last time I noticed one.

However, till you track that down: parties and outings. Arrange the invite screen by relationship, start at the end, and invite up to the desired level, then make sure you have at least one strong positive reaction with each guest. Friendly hugs are great for this, not time-consuming and no jealousy potential. This also has the advantage of encouraging your friends to be friends with each other, good for the party score and also for maintaining their friendship when you play their households! Also, much more fun than just running to the SimBlender.

Phonehack completely gets rid of those notifications.