Google announced today on the official Gmail blog that advanced search in Gmail has been expanded. You can now scour your mail with more flexible date search options, by attachment size, exact query match, and more.
The new syntax works in any version of Gmail, including the Android app, allowing you to use flags like 'size:value' and 'older_than:value' in order to pare down results. For example, below we've used 'size:5m' and 'older_than:1y' to search for mail with attachments of 5MB and that are older than a year, respectively. You can find the full list of advanced search flags here, including the new ones.