Prepositions of Time such as FOR, DURING, WHILE, & SINCE can give English learners a very tough time. I have found that these prepositions are the most commonly misused by French people, for example. They get these prepositions mixed up and it probably has something to do with their own language POUR, PENDANT, DEPUIS, and how those words are interchanged in French, which is a bit different to how they are used in English.
Use “for” to express how long something has been occurring or will occur.
For example: I have been traveling to Spain every summer for the past 15 years.
Use “while” to express 2 actions occurring in roughly the same span of time even though it is unclear how long either of the actions were occurring.
For example: I was eating while I blogged.
Use “during” to express a span of time that has a clear beginning and end that can be objectively measured.
For example: I will get a chin implant during the summer holidays.
(note that the summer holidays can be objectively measured as starting on a specific date and ending on a specific date)
Use “since” to express a moment or time in the past that something such as an activity began. The activity is still going on in the present.
For example: I have been exercising regularly since I was 15.