Bronchiectasis: Given the long history of recurrent hemoptysis without respiratory symptoms, bronchiectasis is a strong consideration. It can cause intermittent bleeding due to damaged airway walls, even in the absence of overt respiratory symptoms.

Pulmonary Arteriovenous Malformations (PAVMs): These abnormal connections between pulmonary arteries and veins can lead to hemoptysis. Their presence could explain the episodic nature of the bleeding.
Mitral Stenosis: Although less common in a 30-year-old without other symptoms, mitral stenosis can lead to hemoptysis due to pulmonary venous hypertension. The lack of respiratory symptoms does not rule out this condition entirely.
Tuberculosis (TB): TB can cause hemoptysis and may not always present with typical respiratory symptoms, especially in its early stages or in individuals with latent TB.

Pulmonary Embolism (PE): Although less likely given the recurrent nature over years, a new onset or change in pattern could suggest a PE, which is life-threatening and requires immediate attention.
Goodpasture Syndrome: An autoimmune disease that can cause recurrent hemoptysis due to anti-GBM antibodies. It's crucial to consider due to its potential for severe outcomes if not treated promptly.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): This vasculitis can cause hemoptysis among other symptoms and has a significant impact on morbidity and mortality if not diagnosed and treated.

Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Syndrome): A genetic disorder that leads to the formation of abnormal blood vessels, which can cause recurrent hemoptysis among other symptoms.
Pulmonary Endometriosis: Endometrial tissue in the lungs can cause cyclical hemoptysis, although this is exceedingly rare.
Catamenial Hemoptysis: Associated with thoracic endometriosis, where hemoptysis occurs in relation to the menstrual cycle, a rare condition that could explain the episodic nature of symptoms in a female patient.

Bronchoscopy: Already scheduled, this will be crucial for directly visualizing the airways and potentially identifying sources of bleeding or other abnormalities.
Imaging: High-resolution CT (HRCT) scan of the chest to evaluate for bronchiectasis, PAVMs, or other structural abnormalities.
Echocardiogram: To assess for mitral stenosis or other cardiac abnormalities that could lead to hemoptysis.
Laboratory Tests: Including complete blood count (CBC), coagulation studies, and tests for autoimmune diseases (e.g., ANCA for GPA, anti-GBM antibodies for Goodpasture syndrome).
Thymoma Workup: Although incidental, the finding of a thymoma requires further evaluation, including potentially a PET scan and discussion about surgical removal, as thymomas can be associated with various systemic and autoimmune conditions.