Is there a time limit for grief?

No...everyone is different and depending what you have going on in your life or if you havn't accepted or the reality of the loss hasn't sunk in, they can have an effect.
Everyone we meet has an impact on us good and bad. When we lose someone who has been a constant in our lives or been a massive influence on us. Sometimes it can be someone who has been in our lives a short time, who can make that lasting impression that it may hurt the most.
For example...a parent or a sibling, who we've been close to for many years, then maybe a disagreement even moving away and just the distance becoming greater, where both sides don't make an effort. A friend or lover who you've been so close to, spent all your time with maybe married or had plans for the future, then a drifting apart..maybe years in some cases. Some of us hear of them passing and really struggle to get over the loss, but is it their loss we struggle with or is it our own feelings of a guilt? Guilt we feel for losing touch, not making an effort as we expected those to? Resentment towards that person for not making an effort as you had hoped or expected? Also the memories come flooding back, of the good times and how much of an impression they were on you. All of these are factors in grief. If you lose someone that you spent a lot of time with, very close to and who were a constant in your life, that hurt will seem to hurt more as they were part of your life there and then! And that is a hurt like no other as that loss is actually happening to you, whereas someone you've drifted apart from, whether by a fall out or just by these things happen, in a sense that loss has already happened and the moving on has taken place naturally.
Losing someone close, is heart wrenching and can take a long time to grieve, memories always come back in many ways.
For me, and for many others im sure, it can hit me when i'm walking along a street and it suddenly hits me that i'm walking along a street that a loved one walked down. Eating a particular food or cooking a certain dish and it hits me how i know how to cook that dish...i've watched a loved one cook it, then it hits me all over again that their influence is still there and ongoing. It hits me how much of an influence they've had on me which i've then passed on to my children. So the generations do cross and i really marvel at that.
It's the same when i hear about someone that i've maybe not seen for a long time for whatever reason, like i said previously, i do feel regret but i also feel the love that was once there and again memories come back, sometimes memories that have long been forgotten.
Rekindle old friendships, family ties and let go of the wounds that have kept you apart. Make the time as that's what we all have in common, we all want more time with those we love.